Critical severity · published Aug 17, 2026
CVE-2026-71424
Onyx: Cross-user OAuth-token leak via /api/mcp/servers* for per-user MCP servers
9.6
CVSS
0.5%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 42% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
ON
onyx · onyx-dot-app
< 3.1.10; >= 3.2.0, < 3.2.14; >= 3.3.0-beta.0, < 4.0.0 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-71424
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-71424
github.com
https://github.com/onyx-dot-app/onyx/commit/3f3d79d1a7722fdc84a1c61c8aa830d890017e9e
github.com
https://github.com/onyx-dot-app/onyx/commit/4001cedd0a8968723bfe95dd188914ed56777910
github.com
https://github.com/onyx-dot-app/onyx/commit/b103937888fd5008067c2bb6eb6e5424576394f2
github.com
https://github.com/onyx-dot-app/onyx/pull/11238
github.com
https://github.com/onyx-dot-app/onyx/pull/11242
github.com
https://github.com/onyx-dot-app/onyx/pull/11243
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