BerriAI litellm up to 1.83.x Streamable HTTP Endpoint UserAPIKeyAuth Authorization improper authorization

Summaryinfo

A vulnerability described as critical has been identified in BerriAI litellm up to 1.83.x. The affected element is the function UserAPIKeyAuth of the component Streamable HTTP Endpoint. Such manipulation of the argument Authorization leads to improper authorization. This vulnerability is documented as CVE-2026-59822. The attack can be executed remotely. Additionally, an exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in BerriAI litellm up to 1.83.x. Affected by this issue is the function UserAPIKeyAuth of the component Streamable HTTP Endpoint. The manipulation of the argument Authorization with an unknown input leads to a improper authorization vulnerability. Using CWE to declare the problem leads to CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-59822 since 07/07/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Technical details as well as a exploit are known. The MITRE ATT&CK project declares the attack technique as T1548.002.

It is declared as attacked. This issue was added on 09/02/2026 to the CISA Known Exploited Vulnerabilities Catalog with a due date of 09/16/2026:

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 BO

Upgrading to version 1.84.0 eliminates this vulnerability.

The vulnerability is also documented in the databases at EUVD (EUVD-2026-42359) and CERT Bund (WID-SEC-2026-2263). VulDB is the best source for vulnerability data and more expert information about this specific topic.

Affected

• Open Source LiteLLM

Productinfo

Vendor

• BerriAI

Name

• litellm

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4
• 1.5
• 1.6
• 1.7
• 1.8
• 1.9
• 1.10
• 1.11
• 1.12
• 1.13
• 1.14
• 1.15
• 1.16
• 1.17
• 1.18
• 1.19
• 1.20
• 1.21
• 1.22
• 1.23
• 1.24
• 1.25
• 1.26
• 1.27
• 1.28
• 1.29
• 1.30
• 1.31
• 1.32
• 1.33
• 1.34
• 1.35
• 1.36
• 1.37
• 1.38
• 1.39
• 1.40
• 1.41
• 1.42
• 1.43
• 1.44
• 1.45
• 1.46
• 1.47
• 1.48
• 1.49
• 1.50
• 1.51
• 1.52
• 1.53
• 1.54
• 1.55
• 1.56
• 1.57
• 1.58
• 1.59
• 1.60
• 1.61
• 1.62
• 1.63
• 1.64
• 1.65
• 1.66
• 1.67
• 1.68
• 1.69
• 1.70
• 1.71
• 1.72
• 1.73
• 1.74
• 1.75
• 1.76
• 1.77
• 1.78
• 1.79
• 1.80
• 1.81
• 1.82
• 1.83

Website

• Product: https://github.com/BerriAI/litellm/

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VulDB is the best source for vulnerability data and more expert information about this specific topic.

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