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.
What to 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.
Affected
BerriAI LiteLLM
all versions prior to 1.84.0 (fixed in 1.84.0)
Estimated exposure
moderateon the order of thousands of internet-exposed LiteLLM gateway instances (estimate; no authoritative total) — Public internet-scan coverage of exposed LiteLLM gateways (e.g., reporting that roughly 1 in 10 exposed gateways accepted the example 'sk-1234' admin key) indicates a scan-visible population in the low thousands, consistent with LiteLLM…
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
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.
CISA Known Exploited Vulnerability
Affected
BerriAI LiteLLM
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.
CISA added seven actively exploited vulnerabilities to its KEV catalog, including SonicWall SMA 1000 SSRF CVE-2026-83548, amid campaigns deploying reverse shells and crypto miners.
CISA's KEV additions cover flaws in SonicWall SMA 1000 (CVE-2026-83548, CVE-2026-83549), Sangoma Switchvox (CVE-2026-9586), JFrog Artifactory (CVE-2026-82329), Kludex Starlette (CVE-2026-48710), Kestra OSS (CVE-2026-49869) and Berri LiteLLM's MCP endpoint (CVE-2026-59822). SonicWall confirmed active exploitation of the SMA 1000 flaws, while Microsoft and Wiz reported attackers chaining LiteLLM flaws CVE-2026-42271 and CVE-2026-48710 to fingerprint hosts, steal provider API keys and deploy XMRig miners on AI infrastructure. Wiz linked exploitation of the LiteLLM chain to the Qilin ransomware group, and Microsoft detailed a Kestra compromise chain ending in cryptocurrency mining and data harvesting via exposed RAGFlow flaws.
Wiz found LiteLLM auth bypass (CVE-2026-59822) and post-auth RCE (CVE-2026-59821) chainable to cloud compromise; the bypass is in CISA KEV with in-the-wild exploitation.
Wiz scanned roughly 3,074 internet-facing LiteLLM deployments and found 9.6% accepted the default master key sk-1234 or required no authentication, making post-auth attacks effectively pre-auth. The MCP endpoint accepts any Bearer token and grants a valid session (CVE-2026-59822), confirmed exploited in the wild via honeypots and added to CISA's Known Exploited Vulnerabilities catalog. Custom code guardrails allow post-auth root-level RCE via exec(compile(...)) (CVE-2026-59821), while pass-through endpoints lack URL validation, enabling cloud credential theft in post-auth scenarios. All assigned vulnerabilities have been patched; the research was presented at DEF CON 34.
Wiz found multiple LiteLLM AI gateway flaws, including a CVE-2026-59822 MCP auth bypass added to CISA KEV, enabling root code execution and cloud credential theft.
An internet scan of 3,074 exposed LiteLLM instances found 294 (9.6%) accepting the default sk-1234 master key and 191 (6.2%) requiring no authentication. CVE-2026-59822 lets a single-character Bearer token establish a valid MCP session via an OAuth2 fallback in versions before 1.84.0; the flaw is in CISA's Known Exploited Vulnerabilities catalog. CVE-2026-59821 allows Python code execution as root in the gateway container via unsanitized Custom Code Guardrails registration before 1.82.0-stable, and CVE-2026-35029 permits config changes leading to RCE and admin takeover. Admin access plus pass-through endpoints can reach cloud metadata services to steal IAM credentials.
CISA added seven actively exploited vulnerabilities to its KEV catalog, including SonicWall SMA1000 SSRF and command injection flaws.
CISA added seven vulnerabilities with evidence of active exploitation to its Known Exploited Vulnerabilities catalog on September 2, 2026. The additions cover Sangoma Switchvox SQL injection (CVE-2026-9586), Kludex Starlette request smuggling (CVE-2026-48710), Kestra OS command injection (CVE-2026-49869), BerriAI LiteLLM (CVE-2026-59822) and JFrog Artifactory (CVE-2026-82329) authentication flaws, and SonicWall SMA1000 SSRF (CVE-2026-83548) and command injection (CVE-2026-83549) vulnerabilities. Under BOD 26-04, federal civilian agencies must prioritize rapid remediation of KEV-listed vulnerabilities on publicly exposed assets.
Wiz disclosed LiteLLM flaws including CVE-2026-59822 MCP auth bypass, now in CISA KEV, enabling root RCE and AWS credential theft from exposed gateways.
Wiz researchers disclosed weaknesses in the open-source LiteLLM AI gateway: CVE-2026-59821 allows authenticated administrators to execute code as root via the Custom Code Guardrails feature, while CVE-2026-59822 is an MCP authentication bypass where a meaningless Bearer token establishes a valid session. The MCP bypass was observed in the wild through Wiz honeypots and added to CISA's Known Exploited Vulnerabilities catalog on September 2. A scan of 3,074 internet-facing instances found 294 (9.6%) accepting the default master key sk-1234 or lacking authentication. Fixes shipped in LiteLLM 1.82.0 (guardrail hardening) and 1.84.0 (MCP bypass); exposed instances can leak provider API keys and temporary AWS IAM credentials via the pass-through feature and metadata service, with a related config-check issue tracked as CVE-2026-35029.
Wiz found 294 of 3,074 internet-facing LiteLLM gateways accepted the documented default admin key sk-1234, exposing provider API keys and cloud IAM credentials.
Wiz Research's February Shodan scan found 3,074 LiteLLM gateways, 294 of which accepted the setup guide's sk-1234 admin key; 191 had no master key set and would accept any credential. The master key doubles as the authentication switch, and before 1.82.0-stable a gateway started without one granted every request full admin rights, exposing stored provider API keys, prompts, and MCP-connected tools. A documented pass-through endpoint lacks checks against private and cloud metadata addresses, letting an admin-key holder retrieve cloud IAM credentials, though no real-world abuse is reported. Related LiteLLM flaws include CVE-2026-59821 (disputed guardrail code execution), CVE-2026-59822 (CVSS 8.8, added to CISA KEV on September 2 and observed against Wiz honeypots), and CVE-2026-42271, used to install a cryptominer.