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40Track*

Authentication bypass in joserfc JSON JWS deserialization

authlib joserfc · CVE-2026-102946 ETK-2026-3058 EUVD-2026-102310 GHSA-4PP3-559J-C5C2
0 news outlets0 CERTs and agencies1 research labs

Assessment: Track*

SSVC decision points: exploitation poc, automatable yes, technical impact total, deployment low.

What is it?

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.7.4, joserfc.jws.deserialize_json() accepts a JWS General JSON Serialization with an empty signatures array as authenticated. The verify_general_json() loop performs no iterations for the empty array and returns success because no signature check failed, allowing an attacker without a signing key to supply an arbitrary payload that relying applications may treat as authentic. The issue affects the General JSON Serialization path; compact JWS and JWT decoding, Flattened JSON serialization, and JWE JSON processing do not follow this vulnerable path. This issue is fixed in version 1.7.4.

Evidence

Technical advisories1Detailed write-ups from security research teams

Exploitation

  • Exploit code published (not verified by us)
  • Exploited in the wild (confirmed by a source)
  • Listed as known exploited (CISA KEV)
CVSS
9.1
EPSS
0.1%
First seen
3 h ago
Status
confirmed

All authlib vulnerabilities