CISA Adds BerriAI LiteLLM Improper Authentication Vulnerability to KEV List

## Overview CISA added CVE-2026-59822 to its Known Exploited Vulnerabilities (KEV) list on September 2, 2026. This vulnerability impacts BerriAI's LiteLLM, a proxy server designed for calling LLM APIs. The addition to the KEV list indicates a federal deadline for remediation, highlighting the urgency of the issue. ## Technical Details The vulnerability exists in LiteLLM's MCP Streamable HTTP endpoint prior to version 1.84.0. An unauthenticated attacker can exploit this flaw by using a fabricated Authorization header. This triggers an OAuth2 passthrough fallback path, which bypasses the standard key validation process. Instead of validating the LiteLLM key, the system uses an empty UserAPIKeyAuth() object. This allows unauthorized requests to access MCP tooling without a valid LiteLLM key. ## Impact The CVSS score for this vulnerability is 8.8, indicating a high severity level. Successful exploitation could allow attackers to establish authenticated MCP sessions using arbitrary Bearer tokens. This could lead to unauthorized access to sensitive resources and functionalities within the LiteLLM environment. ## Mitigation BerriAI has released version 1.84.0 to address this vulnerability. Users are strongly advised to upgrade to this version as soon as possible to protect against potential exploitation. Organizations should also review their security policies and access controls to mitigate risks associated with improper authentication.