pac4j-jwt: JwtAuthenticator Authentication Bypass via JWE-Wrapped PlainJWT
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 software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Java / Kotlin (Maven) | org.pac4j:pac4j-jwt | >= 6.0.4.1, < 6.3.3, >= 5.0.0-RC1, < 5.7.9, < 4.5.9 | 6.3.3, 5.7.9, 4.5.9 |
References
- https://nvd.nist.gov/vuln/detail/CVE-2026-29000
- https://github.com/pac4j/pac4j
- 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
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:L- Weakness (CWE)
CWE-347- Platform
- Java / Kotlin (Maven)
- Package
org.pac4j:pac4j-jwt- Disclosed
- 05.03.2026
- Updated
- 11.10.2026 12:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-pm7g-w2cf-q238 - CC BY 4.0
Vulnerability history: org.pac4j:pac4j-jwt
All published vulnerabilities of this package (Java / Kotlin (Maven)), newest first. Shows whether this is a one-off slip or a package that needs watching.
This is the only known vulnerability of this package.
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