CVE-2026-59822LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback

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.

8.8 HIGHEPSS 0.83%⚡ Known Exploited (CISA KEV)NVD: Analyzed

Last updated: 2026-10-25 17:10 UTC

OverviewCVSS details

8.8HIGHCVSS 4.0

Score source: GitHub_M (CNA)
NVD status: Analyzed
Published: Jul 8, 2026
Assigner: GitHub_M

Affected

litellm (BerriAI)

Versions: < 1.84.0

Exploitation

Public exploit: None listed
CISA KEV: Listed · Sep 2, 2026
KEV due date: Sep 16, 2026
Ransomware use: Unknown
SSVC: Exploitation active · Automatable yes · Impact partial

EPSS · FIRST, scored Nov 7

0.83%chance of exploitation in 30 days

Higher than 57.94% of CVEs

CVSS 4.0 · GitHub_M (CNA)

8.8High

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N

Attack vector: Network
Attack complexity: Low
Attack requirements: None
Privileges required: None
User interaction: None
Confidentiality impact: High
Integrity impact: Low
Availability impact: None
Confidentiality (other systems): None
Integrity (other systems): None
Availability (other systems): None

CVSS 3.1 · NVD

8.2High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: Low
Availability impact: None

NVD status: Analyzed

Overview Affected Products References

NVD CVE.org

Overview

Severity

Score	Severity	Version	Vector String
8.8	HIGH	4.0GitHub_M (CNA)	CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N
8.2	HIGH	3.1NVD	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N

CISA required action

⚡ Known exploited · remediation due Sep 16, 2026

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.

Details

CVE ID: CVE-2026-59822
Status: Analyzed
Assigner (CNA): GitHub_M
Published: Jul 8, 2026
Last modified: 2026-10-25 17:10 UTC
Weaknesses: CWE-287 · Improper Authentication
CWE-306 · Missing Authentication for Critical Function

Sources

Refreshed hourly from the sources above. Last fetched 2026-11-07 16:47 UTC.