Security Digest · Vulnerability record
CVE-2026-29000: 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.
CVSS 9.3 Critical EPSS 0.5% · p43
Should you act?
Critical and remotely reachable
No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Not in CISA KEV, but CISA’s SSVC assessment records a public proof-of-concept, so attack code exists.
- EPSS 0.5%, percentile 43: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 43% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Only applies if your dependency tree includes
org.pac4j:pac4j-jwt(Maven) >= 6.0.4.1, < 6.3.3, fixed in 6.3.3;org.pac4j:pac4j-jwt(Maven) >= 5.0.0-RC1, < 5.7.9, fixed in 5.7.9;org.pac4j:pac4j-jwt(Maven) < 4.5.9, fixed in 4.5.9. Check your lockfile, including transitive dependencies.
What it is
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.
From the GitHub advisory
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.
Weakness type: CWE-347.
Product: org.pac4j:pac4j-jwt (Maven) · Assigned by: VulnCheck · Published: 2026-03-04
Affected and fixed versions
| Ecosystem | Package | Vulnerable | First fixed |
|---|---|---|---|
| Maven | org.pac4j:pac4j-jwt | >= 6.0.4.1, < 6.3.3 | 6.3.3 |
| Maven | org.pac4j:pac4j-jwt | >= 5.0.0-RC1, < 5.7.9 | 5.7.9 |
| Maven | org.pac4j:pac4j-jwt | < 4.5.9 | 4.5.9 |
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| pac4j | pac4j-jwt | 4.0 < 4.5.9, 5.0 < 5.7.9, 6.0 < 6.3.3 |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| VulnCheck | 4.0 | 9.3 Critical | 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 |
| VulnCheck | 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N |
| GitHub | 4.0 | 10.0 | CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:L/SC:H/SI:H/SA:L |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Attack requirements: none
- Privileges required: none (no login)
- User interaction: none
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- CISA SSVC assessment: exploitation poc, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 0.51% probability of exploitation activity in the next 30 days; percentile 43.
Timeline
- — CVE record published by VulnCheck
- — GitHub-reviewed advisory GHSA-pm7g-w2cf-q238 published (critical)
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- pac4j.org pac4j.org
Vulnerability records
- GitHub Advisory GHSA-pm7g-w2cf-q238 github.com
- CVE.org record CVE-2026-29000 cve.org
- NVD entry CVE-2026-29000 nvd.nist.gov
Other references from the CVE record and advisory
- codeant.ai codeant.ai
- vulncheck.com vulncheck.com