GHSA-jjhc-v7c2-5hh6 CVE-2026-35030 PYSEC-2026-390

LiteLLM: Authentication bypass via OIDC userinfo cache key collision

Critical PyPI

Severity: 0.0 / 10; Critical · CVSS 4.0
Exploit chance (EPSS): 0.62%; Chance of exploitation in the next 30 days. Higher than 50.00% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-287 Improper Authentication
Fix: 1.83.0; Upgrade litellm to this version or later

Description

Impact

When JWT authentication is enabled (enable_jwt_auth: true), the OIDC userinfo cache uses token[:20] as the cache key. JWT headers produced by the same signing algorithm generate identical first 20 characters.

This configuration option is not enabled by default. Most instances are not affected.

An unauthenticated attacker can craft a token whose first 20 characters match a legitimate user's cached token. On cache hit, the attacker inherits the legitimate user's identity and permissions. This affects deployments with JWT/OIDC authentication enabled.

Patches

Fixed in v1.83.0. The cache key now uses the full hash of the JWT token.

Workarounds

Disable OIDC userinfo caching by setting the cache TTL to 0, or disable JWT authentication entirely.

Affected versions

PyPI

Package	Vulnerable	Fixed in
litellm	`< 1.83.0`	`1.83.0`
litellm	`< 1.83.0`	`1.83.0`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

litellm PyPI → `1.83.0`

pip

pip install --upgrade "litellm>=1.83.0"

poetry

poetry add "litellm>=1.83.0"

uv

uv add "litellm>=1.83.0"

Severity breakdown

CVSS 4.0 0.0

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

Attack vector: Network
Attack complexity: Low
Attack requirements: Present
Privileges required: None
User interaction: None
Confidentiality (vulnerable system): High
Integrity (vulnerable system): High
Availability (vulnerable system): None
Confidentiality (subsequent systems): High
Integrity (subsequent systems): High
Availability (subsequent systems): None

CVSS 3.1 9.1

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

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

Weakness

CWE-287: Improper Authentication

When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

How to prevent it

Architecture and Design: Use an authentication framework or library such as the OWASP ESAPI Authentication feature.

References

Advisories

Packages

Timeline

Apr 3, 2026 Published
Oct 24, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-7488-6r32-c95q LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback	High Known exploited	Also affects litellm
GHSA-v4p8-mg3p-g94g LiteLLM: Authenticated command execution via MCP stdio test endpoints	High Known exploited	Also affects litellm
GHSA-r75f-5x8p-qvmc LiteLLM has SQL Injection in Proxy API key verification	Critical Known exploited	Also affects litellm
GHSA-g5ff-637f-6q2m LiteLLM: internal_user_viewer arbitrary local file read via `vertex_ai_credentials`	High	Also affects litellm
GHSA-hhww-mrg2-969h LiteLLM vulnerable to reflected XSS in /sso/debug/callback	Medium	Also affects litellm
GHSA-7hp6-4w63-5g45 LiteLLM: Privilege Escalation to Proxy Admin via Cross-Domain Reuse of the Salt Key	Critical	Also affects litellm
GHSA-hx8v-g79f-8w5f LiteLLM Proxy has server-side request forgery via the `user_config` request parameter	Medium	Also affects litellm
GHSA-3cv6-jpf6-8222 LiteLLM: Authenticated SSRF and provider-credential exfiltration via unvalidated request-body routing parameters	Medium	Also affects litellm

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