Pac4J JWT 4.x < 4.5.9 / 5.x < 5.7.9 / 6.x < 6.3.3 Authentication Bypass

critical Nessus Plugin ID 303207

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Synopsis

The remote host has a library that is affected by an authentication bypass vulnerability.

Description

The version of Pac4J JWT installed on the remote host is affected by an authentication bypass vulnerability.

- 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. (CVE-2026-29000)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade Pac4J JWT to version 4.5.9, 5.7.9, 6.3.3, or later based on the installed version branch.

Plugin Details

Severity: Critical

ID: 303207

File Name: pac4j_jwt_CVE-2026-29000.nasl

Version: 1.2

Type: Local

Agent: windows, macosx, unix

Family: Misc.

Published: 3/20/2026

Updated: 3/23/2026

Configuration: Enable thorough checks (optional)

Supported Sensors: Nessus Agent, Nessus

Risk Information

VPR

Risk Factor: High

Score: 7.7

CVSS v2

Risk Factor: High

Base Score: 9.4

Temporal Score: 7.4

Vector: CVSS2#AV:N/AC:L/Au:N/C:C/I:C/A:N

CVSS Score Source: CVE-2026-29000

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 8.2

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:pac4j:pac4j-jwt

Required KB Items: installed_sw/Pac4J JWT

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 3/2/2026

Vulnerability Publication Date: 3/4/2026

Reference Information

CVE: CVE-2026-29000

Detections

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