# CVE-2026-42276: Onyx: IDOR in /chat/stop-chat-session allows any authenticated user to interrupt other users chat sessions

> Authenticated users can interrupt other users' active chat sessions by exploiting a missing ownership check in the stop-chat-session endpoint.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 8 May 2026
- **Updated:** 8 May 2026
- **Also known as:** GHSA-rw6w-hp62-gc8w

## What is CVE-2026-42276?

CVE-2026-42276 is a medium-severity missing authorization vulnerability in onyx-dot-app onyx, published on 8 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Onyx is an open-source AI platform. Prior to versions 3.0.9, 3.1.6, and 3.2.6, the POST /chat/stop-chat-session/{chat_session_id} endpoint lets any authenticated user stop any other user's active chat session. The endpoint checks authentication but never verifies the session belongs to the caller. An attacker who knows a chat session UUID can kill another user's LLM generation mid-stream. This issue has been patched in versions 3.0.9, 3.1.6, and 3.2.6.

Weakness: CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-42276?

It affects 1 product.


Products: Onyx Onyx.

## How do I fix CVE-2026-42276?

No fix has been published for CVE-2026-42276 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-42276 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42276 exists.

## Other vulnerabilities in onyx-dot-app onyx

- [CVE-2026-42277](https://insights.sbomify.com/CVE-2026-42277/): Onyx: IDOR in /chat/file/{file_id} allows any authenticated user to download other users files (medium 6.5)
- [CVE-2024-7767](https://insights.sbomify.com/CVE-2024-7767/): Improper Access Control in danswer-ai/danswer (medium 6.5)
- [CVE-2024-9612](https://insights.sbomify.com/CVE-2024-9612/): Unauthorized Access in danswer-ai/danswer (medium 6.5)
- [CVE-2025-51479](https://insights.sbomify.com/CVE-2025-51479/): Missing authorization in n/a (medium 5.4)
- [CVE-2025-7894](https://insights.sbomify.com/CVE-2025-7894/): Onyx Chat Interface a3_generate_simple_sql.py generate_simple_sql sql injection (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-42276 and fix it if it is affected.

What it is: CVE-2026-42276 is a medium-severity missing authorization vulnerability in onyx-dot-app onyx, published on 8 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-42276 exists.

Affected product: onyx-dot-app onyx. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-42276/ (Markdown: https://insights.sbomify.com/CVE-2026-42276/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42276
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42276
- OSV: https://osv.dev/vulnerability/CVE-2026-42276

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-42276/
Summaries are generated and may contain mistakes; the official description above is the record.