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Critical

LiteLLM: Authentication bypass via OIDC userinfo cache key collision

  • Disclosed: 03.04.2026
  • Updated: 11.10.2026 15:17

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 software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Python (PyPI) litellm < 1.83.0 1.83.0

References

CVSS score -
CVSS vector
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
Weakness (CWE)
CWE-287
Platform
Python (PyPI)
Package
litellm
Disclosed
03.04.2026
Updated
11.10.2026 15:17

Sources and licenses

OSV / GitHub Advisory Database - PYSEC-2026-390 - PyPA Advisory Database; CC BY 4.0

OSV / GitHub Advisory Database - GHSA-jjhc-v7c2-5hh6 - CC BY 4.0

Vulnerability history: litellm

All published vulnerabilities of this package (Python (PyPI)), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (42) in the archive
Total entries
42
First → latest
04.2024 09.2026
Without a fix
14
Exploited in attacks
3

Severity breakdown

  • Critical 7
  • High 17
  • Medium 8
  • Low 9
  • Unrated 1

Disclosures per year

Severity:
  1. LiteLLM vulnerable to server-side template injection in the /prompts/test endpoint
    Critical · 9.8 CVE-2026-37004 < 1.83.7 1.83.7
  2. LiteLLM: MCP Authentication Bypass via OAuth2 Passthrough Fallback
    High Exploited in attacks CVE-2026-59822 < 1.84.0 1.84.0
  3. LiteLLM: Authentication Bypass via Host Header Injection
    Critical · 9.8 CVE-2026-49468 < 1.84.0 1.84.0
  4. LiteLLM allows a user to modify their own user_role via the /user/update endpoint
    High · 8.8 CVE-2026-47102 < 1.83.10 1.83.10
  5. LiteLLM allows an authenticated internal_user to create API keys with access to routes that their role does not permit
    High · 8.8 CVE-2026-47101 < 1.83.14 1.83.14
  6. LiteLLM has a sandbox escape in custom-code guardrail
    High · 8.8 CVE-2026-40217 >= 1.81.8, < 1.83.10 1.83.10
  7. LiteLLM: Authenticated command execution via MCP stdio test endpoints
    High · 8.8 Exploited in attacks CVE-2026-42271 >= 1.74.2, < 1.83.7 1.83.7
  8. LiteLLM has SQL Injection in Proxy API key verification
    Critical · 9.8 Exploited in attacks CVE-2026-42208 >= 1.81.16, < 1.83.7 1.83.7
  9. LiteLLM: Server-Side Template Injection in /prompts/test endpoint
    High CVE-2026-42203 >= 1.80.5, < 1.83.7 1.83.7
  10. LiteLLM: Password hash exposure and pass-the-hash authentication bypass
    High ghsa-69x8-hrgq-fjj8 < 1.83.0 1.83.0
  11. LiteLLM: Authentication bypass via OIDC userinfo cache key collision this entry
    Critical CVE-2026-35030 < 1.83.0 1.83.0
  12. LiteLLM: Privilege escalation via unrestricted proxy configuration endpoint
    High CVE-2026-35029 < 1.83.0 1.83.0
  13. Two LiteLLM versions published containing credential harvesting malware
    Critical ghsa-5mg7-485q-xm76 >= 1.82.7, <= 1.82.8 no fix
  14. LiteLLM Has an Improper Authorization Vulnerability
    High · 8.1 CVE-2025-0628 < 1.61.15 1.61.15
  15. LiteLLM Has a Leakage of Langfuse API Keys
    High · 7.5 CVE-2025-0330 <= 1.52.1 no fix
  16. LiteLLM Reveals Portion of API Key via a Logging File
    High · 7.5 CVE-2024-9606 < 1.44.12 1.44.12
  17. LiteLLM Vulnerable to Denial of Service (DoS) via Crafted HTTP Request
    High · 7.5 CVE-2024-8984 < 1.56.2 1.56.2
  18. LiteLLM Vulnerable to Remote Code Execution (RCE)
    High · 8.8 CVE-2024-6825 >= 1.40.3.dev2, <= 1.40.12 no fix
  19. LiteLLM Vulnerable to Denial of Service (DoS)
    High · 7.5 CVE-2024-10188 < 1.53.1.dev1 1.53.1.dev1
  20. LiteLLM Server-Side Request Forgery (SSRF) vulnerability
    High · 7.5 CVE-2024-6587 < 1.44.8 1.44.8
Show more (4) Showing 20 of 24

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