CVE-2026-42276: Onyx

Medium severity, CVSS 4.3. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Onyx Onyx: before 3.0.9 (fixed in 3.0.9); from 3.1.0, before 3.1.6 (fixed in 3.1.6); from 3.2.0, before 3.2.6 (fixed in 3.2.6)

Published 2026-05-08. Last modified 2026-06-17.