Auth bypass in Onyx
CVE-2026-42276
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.
Vulnerability class: IDOR (Insecure Direct Object Reference)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 4.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L.
EPSS exploit prediction
EPSS: 0.004 (34.6th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 35th percentile — 34.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
- Onyx
- Onyx-Dot-App Onyx — versions < 3.0.9, >= 3.1.0, < 3.1.6, >= 3.2.0, < 3.2.6
Weakness classification (CWE)
References
- github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w (Exploit, Vendor Advisory)
Frequently asked questions
- What is CVE-2026-42276?
- CVE-2026-42276 is a medium-severity vulnerability in Onyx, classified under Authorization Bypass Through User-Controlled Key. CVSS score: 4.3/10. Published 2026-05-08.
- How severe is CVE-2026-42276?
- Medium severity. CVSS v3 base score is 4.3 out of 10.