How severe is CVE-2026-42276?

CVE-2026-42276 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.

Is CVE-2026-42276 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-42276?

CVE-2026-42276 affects Onyx. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-42276?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-42276 have an EU (EUVD) identifier?

Yes. CVE-2026-42276 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28524.

When was CVE-2026-42276 published?

CVE-2026-42276 was published on 2026-05-08 and last updated on 2026-06-17.

CVE-2026-42276

CVE-2026-42276 is a medium-severity vulnerability in Onyx with a CVSS 3.x base score of 4.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-639.

Key facts

Severity: Medium (CVSS 3.x base score 4.3)
EPSS exploit prediction: 0% (20th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-28524
Weakness: CWE-639
Affected product: Onyx
Published: 2026-05-08
Last modified: 2026-06-17

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.

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.
How severe is CVE-2026-42276?: CVE-2026-42276 has a CVSS 3.x base score of 4.3, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability low.
Is CVE-2026-42276 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (20th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-42276?: CVE-2026-42276 affects Onyx. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-42276?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-42276 have an EU (EUVD) identifier?: Yes. CVE-2026-42276 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-28524.
When was CVE-2026-42276 published?: CVE-2026-42276 was published on 2026-05-08 and last updated on 2026-06-17.

References

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

Affected products (1)

cpe:2.3:a:onyx:onyx:*:*:*:*:*:*:*:*

More vulnerabilities in Onyx

CVE-2024-7767 — High (CVSS 8.1): An improper access control vulnerability exists in danswer-ai/danswer version v0.3.94. This vulnerability allows the…
CVE-2026-42277 — Medium (CVSS 6.5): Onyx is an open-source AI platform. Prior to versions 3.0.9, 3.1.6, and 3.2.6, the GET /chat/file/{file_id} endpoint…
CVE-2024-9612 — Medium (CVSS 6.5): In danswer-ai/danswer v0.3.94, administrators can set the visibility of pages within a workspace, including the search…
CVE-2025-7894 — Medium (CVSS 6.3): A vulnerability, which was classified as critical, has been found in Onyx up to 0.29.1. This issue affects the function…
CVE-2025-51479 — Medium (CVSS 5.4): Authorization bypass in update_user_group in onyx-dot-app Onyx Enterprise Edition 0.27.0 allows remote authenticated…

All CVEs affecting Onyx →

Other CWE-639 (Authorization Bypass Through User-Controlled Key (IDOR)) vulnerabilities

CVE-2025-40805 — Critical (CVSS 10.0): Affected devices do not properly enforce user authentication on specific API endpoints. This could facilitate an…
CVE-2024-45032 — Critical (CVSS 10.0): A vulnerability has been identified in Industrial Edge Management Pro (All versions < V1.9.5), Industrial Edge…
CVE-2026-34037 — Critical (CVSS 9.9): Coolify is an open-source and self-hostable tool for managing servers, applications, and databases. Prior to…
CVE-2026-52782 — Critical (CVSS 9.9): OpenProject is open-source, web-based project management software. Prior to 17.3.3 and 17.4.1, there is an IDOR through…
CVE-2026-45552 — Critical (CVSS 9.9): Roxy-WI is a web interface for managing Haproxy, Nginx, Apache and Keepalived servers. In versions 8.2.6.4 and prior,…
CVE-2026-29200 — Critical (CVSS 9.9): A critical IDOR vulnerability has been discovered in Comet Backup affecting all versions from 20.11.0 to 26.1.1 and…

Browse all CWE-639 (Authorization Bypass Through User-Controlled Key (IDOR)) vulnerabilities →