LiteLLM: Authentifizierungsumgehung über Kollision des OIDC-Userinfo-Cache-Schlüssels

The core of this vulnerability lies in how litellm caches user information when JWT (JSON Web Token) authentication is enabled. Specifically, the cache key is derived from only the first 20 characters of the JWT token. Because tokens generated with the same signing algorithm share identical prefixes, an attacker can craft a malicious token whose initial 20 characters match a legitimate user's cached token. Upon a cache hit, the attacker effectively inherits the legitimate user's identity and associated permissions, granting them unauthorized access to the system. The potential impact is significant, ranging from data breaches and unauthorized modifications to complete system compromise, depending on the permissions of the impersonated user.

Organizations using litellm with JWT/OIDC authentication enabled, particularly those with custom JWT generation logic or relying on the library for critical access control. Shared hosting environments where multiple users share the same litellm instance and JWT authentication is enabled are also at increased risk.

• python / supply-chain:

import jwt
# Check for JWT authentication enabled
with open('/path/to/litellm_config.py', 'r') as f:
    for line in f:
        if 'enable_jwt_auth' in line and 'True' in line:
            print('JWT authentication is enabled. Investigate further.')

• generic web:

curl -I https://your-litellm-endpoint/ | grep 'Authorization: Bearer'

• generic web:

# Check access logs for unusual authentication attempts
grep 'Authorization: Bearer' /var/log/nginx/access.log

1. 2026-04-03Disclosure

   disclosure

1. Reserviert2026-03-31
2. Veröffentlicht2026-04-03
3. Geändert2026-04-08
4. EPSS aktualisiert2026-04-14

The primary mitigation for CVE-2026-35030 is to upgrade to version 1.83.0 or later, which addresses the flawed cache key generation. If an immediate upgrade is not feasible due to compatibility concerns or breaking changes, consider temporarily disabling JWT authentication if it is not essential. Alternatively, implement stricter token validation rules to prevent the use of tokens with predictable prefixes. Monitor logs for unusual authentication patterns or attempts to access resources with unexpected identities. After upgrading, confirm the fix by attempting to authenticate with a crafted token and verifying that authentication fails.