Authlib Signature Verification Bypass Vulnerability

Executive Summary

Authlib versions 1.7.2 and below contain a signature verification bypass flaw in the JsonWebSignature.deserialize_json() method. This method accepts a JSON Serialization JWS object and returns the payload as verified without checking for a signature or requiring a cryptographic key.

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Detection Guidance

Check if your system uses Authlib versions 1.7.2 or below by inspecting installed packages. For Python, run: pip show authlib. If vulnerable, look for applications using JWS deserialization methods like jws.deserialize_json() or jws.deserialize() with empty signatures arrays.

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Impact Analysis

Attackers can forge arbitrary content without a signing key, bypassing authentication and authorization checks. This may lead to authentication bypass, privilege escalation, forged authorization claims, or integrity bypass in microservices using Authlib for JWS verification.

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Compliance Impact

This vulnerability could undermine compliance with GDPR and HIPAA by allowing unauthorized access to sensitive data or systems. Authentication bypass may lead to unauthorized data exposure or modification, violating integrity and confidentiality requirements.

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Mitigation Strategies

Monitor the Authlib GitHub repository for patches and upgrade to the latest version once available. Avoid using JWS deserialization methods with empty signatures arrays. If immediate mitigation is needed, consider disabling JWS verification or switching to alternative libraries until a fix is released.

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