MSRXCVE-2026-59822
CVE-2026-59822
LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
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.
CVSS 4.0 · CNA
chance of exploitation in the next 30 days (EPSS; higher than 57% of CVEs)
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.
Affected packages and fixed versions
| Package | Ecosystem | Fixed in |
|---|---|---|
| litellm | PyPI | 1.84.0 |
Affected products
- BerriAI litellm: < 1.84.0
Also known as: GHSA-7488-6r32-c95q, PYSEC-2026-3479
4 references (advisories, patches, write-ups)
- https://github.com/BerriAI/litellm/security/advisories/GHSA-7488-6r32-c95q · x_refsource_CONFIRM
- https://github.com/BerriAI/litellm/pull/26463 · x_refsource_MISC
- https://github.com/BerriAI/litellm/commit/73869f0faf7d11ee21adcb5f91b8c33a340b6c2c · x_refsource_MISC
- https://github.com/BerriAI/litellm/releases/tag/v1.84.0 · x_refsource_MISC
Sources: CVE.org, OSV.dev, FIRST EPSS. Missing ones did not answer or have no record yet.