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PatchSiren cyber security CVE debrief

CVE-2026-29000 pac4j CVE debrief

CVE-2026-29000 is an authentication bypass vulnerability in pac4j-jwt versions prior to 4.5.9, 5.7.9, and 6.3.3. The vulnerability is located in JwtAuthenticator when processing encrypted JWTs, allowing 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. This vulnerability has a high impact on system security and integrity.

Vendor
pac4j
Product
pac4j-jwt
CVSS
CRITICAL 9.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-03-04
Original CVE updated
2026-07-14
Advisory published
2026-03-04
Advisory updated
2026-07-14

Who should care

Users of pac4j-jwt versions prior to 4.5.9, 5.7.9, and 6.3.3 should be aware of this authentication bypass vulnerability and take steps to remediate. This includes operators, administrators, and security teams responsible for maintaining and securing systems that utilize pac4j-jwt for authentication.

Technical summary

The CVE-2026-29000 vulnerability is caused by a flaw in JwtAuthenticator when processing encrypted JWTs. This allows an attacker with the server's RSA public key to create a JWE-wrapped PlainJWT with arbitrary claims, effectively bypassing signature verification. As a result, an attacker can authenticate as any user, including administrators, without proper authentication. The vulnerability affects pac4j-jwt versions prior to 4.5.9, 5.7.9, and 6.3.3, and has a high impact on system security and integrity.

Defensive priority

High

Recommended defensive actions

  • Upgrade pac4j-jwt to version 4.5.9, 5.7.9, or 6.3.3 or later
  • Restrict access to the server's RSA public key
  • Implement additional authentication mechanisms
  • Monitor for suspicious authentication activity
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE-2026-29000 vulnerability was reported by Codeant. The NVD entry for CVE-2026-29000 provides additional details on the vulnerability. Evidence is limited to public sources and may not reflect the full scope or impact of the vulnerability. Defenders should verify affected systems and review official advisories for specific guidance.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-29000 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-29000

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-29000 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-29000

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.