CVE-2026-42276: Onyx is an open-source AI platform

Routine

MEDIUM 4.3UPGRADE

CVE-2026-42276 is a medium-severity flaw (CVSS 4.3) affecting onyx. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	4.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 80%)
CISA exploited list	No
Weakness	CWE-639
Published	2026-05-08
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: onyx

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-08 05:16 UTCPublished CVE record published
2026-06-17 10:47 UTCUpdated Record last modified

onyx onyx UPGRADE

Affected: < 3.0.9 · >= 3.1.0 and < 3.1.6 · >= 3.2.0 and < 3.2.6

Fixed in: 3.0.9, 3.1.6, 3.2.6

Safe to downgrade to: a release before 3.1.0

1. Check installed version

apt-cache policy onyx || rpm -q onyx || onyx --version

2. UPGRADE to 3.0.9 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade onyx

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade onyx

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 3.1.0 (Debian / Ubuntu)

apt-cache madison onyx sudo apt install onyx=<VERSION_BEFORE_3.1.0> sudo apt-mark hold onyx

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list onyx sudo dnf downgrade onyx-<VERSION_BEFORE_3.1.0> sudo dnf versionlock add onyx

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42276?

onyx: upgrade to 3.0.9, 3.1.6, 3.2.6. Exact commands for each OS are on this page.

Is CVE-2026-42276 being exploited?

CVE-2026-42276 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42276 affect?

CVE-2026-42276 affects onyx. Severity is medium (CVSS 4.3). 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 authentica

How urgent is CVE-2026-42276?

Priority 25/100. Public exploit reference

Related CVEs

CVE-2026-42277 MEDIUM 6.5 UPGRADE Onyx is an open-source AI platform

References

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