CVE-2026-102946

CRITICAL 9.1

joserfc: JWS signature verification bypass via empty signatures array in jws.deserialize_json

CVSS Score

9.1

EPSS Score

0.0%

EPSS Percentile

0th

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.

CWE	CWE-290 CWE-345 CWE-347
Vendor	authlib
Product	joserfc
Published	Oct 15, 2026

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CVSS v3 Breakdown

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Affected Versions

authlib / joserfc

< 1.7.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/authlib/joserfc/security/advisories/GHSA-4pp3-559j-c5c2 github.com: https://github.com/authlib/joserfc/commit/f409f8f058225d7686acab6546c94593e4c1bfbe github.com: https://github.com/authlib/joserfc/releases/tag/1.7.4