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

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

Which versions are affected by CVE-2026-42276?

It affects 1 product.

Products include 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.

Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.

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 Onyx: IDOR in /chat/file/{file_id} allows any authenticated user to download other users files Medium 6.5
• CVE-2024-7767 Improper Access Control in danswer-ai/danswer Medium 6.5
• CVE-2024-9612 Unauthorized Access in danswer-ai/danswer Medium 6.5
• CVE-2025-51479 Missing authorization in n/a Medium 5.4
• CVE-2025-7894 Onyx Chat Interface a3_generate_simple_sql.py generate_simple_sql sql injection Medium 5.3

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-rw6w-hp62-gc8w.