What is CVE-2026-29000?

CVE-2026-29000 is a critical-severity vulnerability in Pac4j Pac4j-Jwt, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.1/10. Published 2026-03-04.

How severe is CVE-2026-29000?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Is CVE-2026-29000 known to be exploited?

24 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Pac4j Pac4j-Jwt

CVE-2026-29000

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.

Published 2026-03-04 · last modified 2026-07-14.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

EPSS exploit prediction

EPSS: 0.005 (39.2th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 39th percentile — 39.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.059 · newest: 0.005 · change: -0.054

Affected products

Pac4j Pac4j-Jwt — versions 4.0, 5.0, 6.0

Weakness classification (CWE)

CWE-347 — Improper Verification of Cryptographic Signature

Public proof-of-concept exploits

References

www.pac4j.org/blog/security-advisory-pac4j-jwt-jwtauthenticator.html (vendor-advisory)
www.codeant.ai/security-research/pac4j-jwt-authentication-bypass-public-key (technical-description, exploit)
www.vulncheck.com/advisories/pac4j-jwt-jwtauthenticator-authentication-bypass (third-party-advisory)

Frequently asked questions

What is CVE-2026-29000?: CVE-2026-29000 is a critical-severity vulnerability in Pac4j Pac4j-Jwt, classified under Improper Verification of Cryptographic Signature. CVSS score: 9.1/10. Published 2026-03-04.
How severe is CVE-2026-29000?: Critical severity. CVSS v3 base score is 9.1 out of 10.
Is CVE-2026-29000 known to be exploited?: 24 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.