Critical Info disclosure

CVE-2026-71424 — Onyx: Cross-user OAuth-token leak via /api/mcp/servers* for per-user MCP servers

Onyx is an open-source AI platform. Prior to 3.1.10, 3.2.14, and 4.0.0, Onyx's GET /api/mcp/servers and GET /api/mcp/servers/persona/{persona_id} endpoints expose another user's OAuth Authorization header because OnyxTokenStorage.set_tokens and OnyxTokenStorage.set_client_info in backend/onyx/server/features/mcp/api.py copy per-user tokens into a shared admin MCPConnectionConfig row and _db_mcp_server_to_api_mcp_server returns that row through auth_template.headers to any BASIC_ACCESS user. This issue is fixed in versions 3.1.10, 3.2.14, and 4.0.0.

Published Aug 17, 2026 · Updated Oct 15, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

Technical severity (critical)+10

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

—

No EPSS score.

Affects

Onyx-dot-app

Onyx

CVSS base

9.6

Critical · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Onyx-dot-app Onyx).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (info disclosure), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Onyx-dot-app	Onyx	version < 3.1.10version >= 3.2.0, < 3.2.14version >= 3.3.0-beta.0, < 4.0.0	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Changed

Confidentiality

High

Integrity

High

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
9.6	CVSS 3.1	Critical	3.1	5.8	security-advisories@github.com via NIST National Vulnerability Database
9.6	CVSS 3.1	Critical	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N (score shown at the top: security-advisories@github.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-200 · Exposure of Sensitive Information

Other CVEs with this weakness →

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Look for anomalous data read/export volumes and access to sensitive records.

web/proxy/WAF logsnetwork IDS/IPSapplication logsauthentication logs

Timeline

What happened to this CVE, newest first.

2026
Affected products added · onyx-dot-app/onyx
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 15, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 15, 2026
CVSS changed · 9.6
Oct 15, 2026 · NIST National Vulnerability Database
Source status changed · → Deferred
Oct 15, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 15, 2026 · NIST National Vulnerability Database
CVE published
Aug 17, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 15, 2026 – Oct 15, 2026

References

8 on the record

github.com/onyx-dot-app/onyx/pull/11242
x_refsource_MISC, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/commit/b103937888fd5008067c2bb6eb6e5424576394f2
x_refsource_MISC, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/commit/4001cedd0a8968723bfe95dd188914ed56777910
x_refsource_MISC, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/pull/11243
x_refsource_MISC, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/pull/11238
x_refsource_MISC, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/releases/tag/v4.0.0
x_refsource_MISC, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/security/advisories/GHSA-q62f-rv3h-f822
x_refsource_CONFIRM, NIST National Vulnerability Database
github.com/onyx-dot-app/onyx/commit/3f3d79d1a7722fdc84a1c61c8aa830d890017e9e
x_refsource_MISC, NIST National Vulnerability Database

Elsewhere on this site

Onyx-dot-app
every CVE for this vendor

Info disclosure
same class

CWE-200
other pages naming this weakness

Related CVEs (same products)

Medium CVE-2026-85700 Onyx 4.6.6 Custom Tool Secret Header Disclosure via Tool Endpoints Sep 4, 2026
Medium CVE-2026-63178 Onyx Curator-scope IDOR: any curator can modify membership of arbitrary user groups via unscoped PATCH /manage/admin/user-group/{id} and /add-users leading to cross-group document disclosure Aug 17, 2026
Medium CVE-2026-42276 Onyx: IDOR in /chat/stop-chat-session allows any authenticated user to interrupt other users chat sessions May 8, 2026
Medium CVE-2026-42277 Onyx: IDOR in /chat/file/{file_id} allows any authenticated user to download other users files May 8, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No FIRST EPSS score.
No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-71424 is "Onyx: Cross-user OAuth-token leak via /api/mcp/servers* for per-user MCP servers", rated Critical. It affects Onyx (Onyx-dot-app); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.6 describes technical severity. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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