CVE-2026-42276

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.

CVSS v3.1 Score

4.3

MEDIUM

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0005

Probability of exploitation

0.14%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

Affected Products

Vendor	Product	Versions
onyx	onyx	< 3.0.9
onyx	onyx	3.1.0 — 3.1.6
onyx	onyx	3.2.0 — 3.2.6

References

Advisories & Patches

https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w

Exploits

https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 4.3 (MEDIUM).

How severe is CVE-2026-42276? +

CVE-2026-42276 has a CVSS v3.1 score of 4.3 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0005, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42276? +

CVE-2026-42276 affects products from onyx, specifically: onyx. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42276? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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