CVE-2025-62706: authlib Uncontrolled Resource Consumption

Vulnerability summary

CVE-2025-62706 is a medium (CVSS 6.5) Uncontrolled Resource Consumption vulnerability in authlib. EPSS estimates a 0.46% chance of exploitation in the next 30 days, higher than 38.3% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 22-10-2025
   PublishedVulnerability first disclosed.
2. 03-11-2025
   Last modifiedVulnerability information updated.

Description

Authlib is a Python library which builds OAuth and OpenID Connect servers. Prior to version 1.6.5, Authlib’s JWE zip=DEF path performs unbounded DEFLATE decompression. A very small ciphertext can expand into tens or hundreds of megabytes on decrypt, allowing an attacker who can supply decryptable tokens to exhaust memory and CPU and cause denial of service. This issue has been patched in version 1.6.5. Workarounds for this issue involve rejecting or stripping zip=DEF for inbound JWEs at the application boundary, forking and add a bounded decompression guard via decompressobj().decompress(data, MAX_SIZE)) and returning an error when output exceeds a safe limit, or enforcing strict maximum token sizes and fail fast on oversized inputs; combine with rate limiting.

• CWE-400Uncontrolled Resource ConsumptionThe product does not properly control the allocation and maintenance of a limited resource.
• CWE-770Allocation of Resources Without Limits or ThrottlingThe product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.