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CVE

CVE-2026-59822

LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
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CVE

CVE-2026-59822

LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. Prior to 1.84.0, LiteLLM's MCP Streamable HTTP endpoint allowed an unauthenticated attacker to use a fabricated Authorization header to trigger an OAuth2 passthrough fallback path that replaced failed LiteLLM key validation with an empty UserAPIKeyAuth() object, allowing requests to reach MCP tooling without a valid LiteLLM key. This issue is fixed in version 1.84.0.

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
8.8
-
4.0
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
C
H
U
0
-
C
H
U
-

Related Resources

No items found.

References

https://github.com/BerriAI/litellm/releases/tag/v1.84.0, https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-59822, https://github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q, https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59822.json, https://nvd.nist.gov/vuln/detail/CVE-2026-59822, https://www.wiz.io/blog/ai-infrastructure-honeypot, https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c, https://github.com/BerriAI/litellm/pull/26463

Severity

0

CVSS Score
0
10

Basic Information

Base CVSS
0
EPSS Probability
0.00516%
EPSS Percentile
0.41918%
Introduced Version
0
Fix Available
73869f0faf7d11ee21adcb5f91b8c33a340b6c2c

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