High severity · published Jul 8, 2026
CVE-2026-59822
LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
In wildKEV
8.2
CVSS
0.8%
EPSS
Yes
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
High
Integrity
Low
Availability
None
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.8% · higher than 58% of CVEs
Exploited in the wildYes
CISA KEVListed Sep 2, 2026
Federal remediation dueSep 16, 2026
Ransomware campaign useNot known
Affected products
Which versions
LI
litellm · BerriAI
< 1.84.0 · source: vendor, NVD, KEV
In the news
AdvisoryHigh
CISA Adds Seven Known Exploited Vulnerabilities to Catalog
CISA has added seven new vulnerabilities to its Known Exploited Vulnerabilities (KEV) Catalog , based on evidence of active exploitation. &nbsp; CVE-2026-9586 Sangoma Switchvox SQL Injection Vulnerability&nbsp; CVE-2026-48710 Kludex Starlette HTTP Request/Response Smuggling Vulnerability&nbsp; CVE-2026-49869 Kestra OSS OS Command Injection Vulnerability&nbsp; CVE-2026-59822 BerriAI LiteLLM Improper Authentication Vulnerability&nbsp; CVE-2026-82329 JFrog Artifactory Improper Authentication Vulnerability&nbsp; CVE-2026-83548 SonicWall SMA1000 Appliances Server-Side Request Forgery Vulnerability&nbsp; CVE-2026-83549 SonicWall SMA1000 Appliances OS Command Injection Vulnerability&nbsp; These types of vulnerabilities are a frequent attack vector for malicious cyber actors and pose significant risks to the federal enterprise.&nbsp; Binding Operational Directive (BOD) 26-04: Prioritizing Security Updates Based on Risk establishes vulnerability management requirements for Federal Civilian Executive Branch (FCEB) agencies. BOD 26-04 reinforces the importance of the KEV Catalog and requires federal agencies to prioritize rapid remediation of high-risk vulnerabilities, specifically those identified by Common Vulnerabilities and Exposures (CVEs) listed in CISA’s KEV Catalog on publicly exposed assets that grant total control of the asset post-exploitation, while deferring action f...
Sep 2, 2026·CISA Advisories
VulnerabilityHigh
[CISA KEV] CVE-2026-59822: BerriAI LiteLLM - BerriAI LiteLLM Improper Authentication Vulnerability
BerriAI LiteLLM contains an improper authentication vulnerability in the MCP Streamable HTTP endpoint that could allow an unauthenticated attacker to establish an authenticated MCP session using an arbitrary Bearer token.
Sep 2, 2026·CISA KEV