Authlib up to 1.6.4 Decompression decompress resource consumption

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Authlib up to 1.6.4. This affects the function decompress of the component Decompression Handler. This manipulation causes resource consumption. This vulnerability is tracked as CVE-2025-62706. The attack is possible to be carried out remotely. No exploit exists. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in Authlib up to 1.6.4. Affected by this vulnerability is the function decompress of the component Decompression Handler. The manipulation with an unknown input leads to a resource consumption vulnerability. The CWE definition for the vulnerability is CWE-400. The product does not properly control the allocation and maintenance of a limited resource, thereby enabling an actor to influence the amount of resources consumed, eventually leading to the exhaustion of available resources. As an impact it is known to affect availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2025-62706 since 10/20/2025. The exploitation appears to be easy. The attack can be launched remotely. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1499 for this issue.

The vulnerability scanner Nessus provides a plugin with the ID 271720 (Linux Distros Unpatched Vulnerability : CVE-2025-62706), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.6.5 eliminates this vulnerability. Applying the patch e0863d5129316b1790eee5f14cece32a03b8184d is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

The vulnerability is also documented in the databases at Tenable (271720), EUVD (EUVD-2025-33799) and CERT Bund (WID-SEC-2026-0120). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Affected

• Red Hat Satellite

Productinfo

Name

• Authlib

Version

• 1.6.0
• 1.6.1
• 1.6.2
• 1.6.3
• 1.6.4

License

• open-source

Website

• Product: https://github.com/authlib/authlib/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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