CVE-2026-29000: PAC4J PAC4J-Jwt

Critical severity, CVSS 9.1. EPSS: 0.5% chance of exploitation in the next 30 days.

pac4j-jwt versions prior to 4.5.9, 5.7.9, and 6.3.3 contain an authentication bypass vulnerability in JwtAuthenticator when processing encrypted JWTs that allows remote attackers to forge authentication tokens. Attackers who possess the server's RSA public key can create a JWE-wrapped PlainJWT with arbitrary subject and role claims, bypassing signature verification to authenticate as any user including administrators.

Affected products

• PAC4J PAC4J-Jwt: from 4.0, before 4.5.9 (fixed in 4.5.9); from 5.0, before 5.7.9 (fixed in 5.7.9); from 6.0, before 6.3.3 (fixed in 6.3.3)

Published 2026-03-04. Last modified 2026-10-08.