CVE-2026-59822: LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
In CISA’s Known Exploited Vulnerabilities catalog: BerriAI LiteLLM Improper Authentication Vulnerability.
Added , federal remediation due . Known ransomware use: Unknown.
Required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
Description
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.
Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N · CWE-287, CWE-306
Status incidents that name it
No tracked status incident names this CVE.
Affected vendors and products
BerriAI: litellm
References
- CVE record on cve.org (opens in new tab)
- NVD entry (opens in new tab)
- github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c (opens in new tab)
- github.com/BerriAI/litellm/pull/26463 (opens in new tab)
- github.com/BerriAI/litellm/releases/tag/v1.84.0 (opens in new tab)
- github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q (opens in new tab)
- CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (opens in new tab)
- This product uses data from the NVD API but is not endorsed or certified by the NVD. (opens in new tab)
- Known Exploited Vulnerabilities catalog from CISA. (opens in new tab)
- EPSS scores from FIRST (Exploit Prediction Scoring System). (opens in new tab)