# 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.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 11 May 2026
- **Updated:** 12 May 2026
- **Also known as:** GHSA-ghcv-22jf-vfxm

## 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 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-43874?

2 open source packages ship an affected version, including wwbn/avideo.


| Package | Ecosystem | 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.

## Is CVE-2026-43874 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43874 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43874 and fix it if it is affected.

What it is: 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.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43874 exists.

Affected packages and fixed versions:
- wwbn/avideo (Packagist): affected all versions up to 29.0; no fix listed
- wwbn/avideo (Packagist): affected all versions up to 29.0; no fix listed

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-43874/ (Markdown: https://insights.sbomify.com/CVE-2026-43874/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43874
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43874
- OSV: https://osv.dev/vulnerability/CVE-2026-43874

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-43874/
Summaries are generated and may contain mistakes; the official description above is the record.