LiteLLM AI Gateway Flaws Enable Root Code Execution and Cloud Credential Theft; MCP Auth Bypass Added to CISA KEV

CVE-2026-35029 is a broken access control flaw (CWE-863, CWE-425) in LiteLLM, an open-source proxy server (AI Gateway) for calling LLM APIs, in which the /config/update endpoint fails to enforce admin-role authorization in versions prior to 1.83.0. Any user who is already authenticated to the proxy can call this network-accessible endpoint without admin rights and modify the proxy configuration and environment variables. Through this, an attacker can achieve remote code execution by registering pass-through endpoint handlers that point to attacker-controlled Python code, read arbitrary server files by setting UI_LOGO_PATH and fetching the file via /get_image, and take over other privileged accounts by overwriting the UI_USERNAME and UI_PASSWORD environment variables; related security coverage also highlights that vulnerable LiteLLM gateways can be turned into root-level code execution and cloud credential theft. Any organization running a LiteLLM proxy older than v1.83.0 is affected, particularly deployments where non-admin users hold authenticated accounts. No public proof-of-concept or confirmed in-the-wild exploitation is known and the flaw is not in CISA KEV, but EPSS assigns a 25.1% probability of exploitation within 30 days (98th percentile), signaling elevated near-term risk.

Do: Upgrade to LiteLLM v1.83.0 or later. Until patched, restrict network access to /config/update so only administrators can reach it, and limit how many non-admin accounts hold API/UI credentials on the proxy. Audit configuration and environment variables for tampering (especially UI_USERNAME, UI_PASSWORD, UI_LOGO_PATH, and registered pass-through handlers), and rotate cloud credentials stored in the gateway's environment if compromise is suspected.

LiteLLM is a proxy server (AI Gateway) to call LLM APIs in OpenAI (or native) format. Prior to 1.82.0-stable, LiteLLM's Custom Code Guardrails production create and update paths did not apply the same sandboxing and validation used by the test endpoint, allowing a privileged user with access to create or update guardrails to submit custom Python code that executed in the LiteLLM proxy environment and could expose secrets available to the process. This issue is fixed in version 1.82.0-stable.

BerriAI LiteLLM, a widely used self-hosted AI gateway and proxy server for calling LLM APIs, fails to properly authenticate requests to its MCP Streamable HTTP endpoint in versions prior to 1.84.0. An unauthenticated attacker can send a fabricated Authorization header that triggers an OAuth2 passthrough fallback, which replaces failed LiteLLM key validation with an empty UserAPIKeyAuth() object and lets the request reach MCP tooling without any valid LiteLLM key. Successful exploitation grants unauthenticated access to the gateway's MCP tooling with high confidentiality impact per the CVSS 4.0 score of 8.8, and public reporting describes attackers chaining LiteLLM weaknesses from authentication bypass to root code execution and cloud credential theft. Any organization running LiteLLM before 1.84.0 is affected, particularly gateways exposed to the internet. The flaw is confirmed exploited in the wild: CISA added it to the Known Exploited Vulnerabilities catalog on 2026-09-02, while EPSS currently estimates a 0.9% probability of exploitation in the next 30 days.

Do: Upgrade LiteLLM to version 1.84.0 or later immediately, in line with the CISA KEV required action and BOD 26-04 guidance for internet-exposed assets. Audit whether the MCP endpoint is reachable from the internet and check for signs of exploitation, including unexpected MCP tool calls, use of fabricated Authorization headers, and use of default or example admin keys such as 'sk-1234'. Until patched, restrict access to the MCP endpoint and review cloud credentials accessible from the gateway host for signs of theft or root-level activity.