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Vulnerability record · CVE-2026-29000 · published 4 March 2026

CVE-2026-29000: Improper verification of cryptographic signature vulnerability

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.

9.3 CVSS 4.0 Critical EPSS 0.48% · top 60.8% CWE-347 · Improper verification of cryptographic signature Deferred
9.3CVSS 4.0 base score
0.48%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
14 Jul 2026Last modified by NVD

Description

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.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://www.codeant.ai/security-research/pac4j-jwt-authentication-bypass-public-key
https://www.pac4j.org/blog/security-advisory-pac4j-jwt-jwtauthenticator.html
https://www.vulncheck.com/advisories/pac4j-jwt-jwtauthenticator-authentication-bypass

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Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2026-29000), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.