# CVE-2026-29000: pac4j-jwt authentication bypass in JwtAuthenticator

Source: https://junglewise.ai/threats/cve-2026-29000-pac4j-jwt-authentication-bypass-in-jwtauthenticator  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-03-04. Updated: 2026-07-14  
License: CC BY 4.0 with a link back

CVE-2026-29000 · Severity: critical · CVSS 9.1 · Published 2026-03-04

A security flaw in the pac4j-jwt library, which handles user authentication for Java applications, allows attackers to bypass security checks. By exploiting this issue, an unauthorized person can create fake login credentials to gain full access to the system, including administrative privileges. This could lead to the theft of sensitive customer data or complete control over the affected application.

Vendors: [Maven](https://junglewise.ai/threats/vendors/maven), [Pac4j](https://junglewise.ai/threats/vendors/pac4j).

## Quick answers

**Is CVE-2026-29000 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-29000 being exploited in the wild.

**How severe is CVE-2026-29000?** Critical severity, with a CVSS score of 9.1, published 4 March 2026.

**Which products and versions are affected?** org.pac4j:pac4j-jwt (Maven) ECOSYSTEM:introduced=6.0.4.1,fixed=6.3.3; Pac4j-Jwt >= 4.0, < 4.5.9; >= 5.0, < 5.7.9; >= 6.0, < 6.3.3.

**Is there a fix for CVE-2026-29000?** Yes. org.pac4j:pac4j-jwt (Maven): upgrade to 6.3.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-29000 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-29000?** Check whether you run org.pac4j:pac4j-jwt (Maven) or Pac4j-Jwt at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.pac4j:pac4j-jwt (Maven): upgrade to 6.3.3 or later

  ```sh
  # set org.pac4j:pac4j-jwt to 6.3.3 in your pom.xml or build.gradle
  ```


## Technical details

An authentication bypass vulnerability exists in the JwtAuthenticator component of pac4j-jwt due to improper verification of cryptographic signatures (CWE-347) when processing encrypted JSON Web Tokens (JWTs). Specifically, the library fails to properly validate the signature of a PlainJWT when it is wrapped within a JSON Web Encryption (JWE) structure. A remote, unauthenticated attacker who possesses the server's RSA public key can craft a malicious JWE-wrapped token containing arbitrary subject and role claims. This allows the attacker to bypass signature verification entirely and authenticate as any user, including administrators. The issue is resolved in versions 4.5.9, 5.7.9, and 6.3.3.

## Affected products

- pac4j pac4j-jwt >= 4.0, < 4.5.9; >= 5.0, < 5.7.9; >= 6.0, < 6.3.3

## Identifiers

- CVE-2026-29000
- GHSA-pm7g-w2cf-q238

## Timeline

- 2026-03-04: advisory: Initial disclosure by VulnCheck and NVD
- 2026-03-04: patched: Fixes released in versions 4.5.9, 5.7.9, and 6.3.3

## References

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