CVE-2026-43874 AVideo has an Incomplete Fix for YPTSocket autoEvalCodeOnHTML Strip: Unauthenticated Cross-User JavaScript Execution via `$msg['json']` Relay Bypass
Unauthenticated attackers can execute arbitrary JavaScript in logged-in users' browsers via a WebSocket relay bypass in WWBN AVideo.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-43874?
CVE-2026-43874 is a high-severity cross-site scripting vulnerability in WWBN AVideo, published on 11 May 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
WWBN AVideo is an open source video platform. In versions up to and including 29.0, the server-side mitigation for the YPTSocket autoEvalCodeOnHTML eval sink (from CVE-2026-40911) only strips the payload when it sits under $json['msg'], but the relay function msgToResourceId() selects the outbound message from $msg['json'] before $msg['msg']. An unauthenticated attacker can obtain a WebSocket token from plugin/YPTSocket/getWebSocket.json.php, connect to the WebSocket server, and send a message with autoEvalCodeOnHTML nested under a top-level json field — the strip branch is skipped, the relay delivers the payload verbatim to any logged-in user identified by to_users_id, and the client script runs it through eval(). Commit 9f3006f9a89a34daa67a83c6ad35f450cb91fcce contains an updated fix.
Weakness: CWE-94
Which versions are affected by CVE-2026-43874?
2 open source packages ship an affected version, including wwbn/avideo.
| Package | Affected | Fixed in |
|---|---|---|
wwbn/avideo Packagist | All versions to 29.0 | None |
wwbn/avideo Packagist | All versions to 29.0 | None |
How do I fix CVE-2026-43874?
No fix has been published for CVE-2026-43874 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-43874 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43874 exists.
Sources
Also known as GHSA-ghcv-22jf-vfxm.