Vulnerability · Published Oct 15, 2026 · Assigned by GitHub_M
CVE-2026-102946joserfc: JWS signature verification bypass via empty signatures array in jws.deserialize_json
Critical 9.1
In plain English
A critical-severity authentication bypass by spoofing in joserfc from authlib. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.1% (higher than 2% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:13 | joserfc | no fix listed | DEBIAN-CVE-2026-102946 |
| Debian:14 | joserfc | 1.7.4-1 | DEBIAN-CVE-2026-102946 |
| Ubuntu:26.04:LTS | joserfc | no fix listed | UBUNTU-CVE-2026-102946 |
| Ubuntu:26.10 | joserfc | no fix listed | UBUNTU-CVE-2026-102946 |
Affected products (as reported)
Weakness: CWE-290, CWE-345, CWE-347 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
References
- https://github.com/authlib/joserfc/security/advisories/GHSA-4pp3-559j-c5c2 x_refsource_CONFIRM
- https://github.com/authlib/joserfc/commit/f409f8f058225d7686acab6546c94593e4c1bfbe x_refsource_MISC
- https://github.com/authlib/joserfc/releases/tag/1.7.4 x_refsource_MISC