pac4j-oidc before 6.5.6 Authentication Bypass via Access Token Substitution

Advisories

pac4j-oidc before 6.5.6 Authentication Bypass via Access Token Substitution

severity: medium
date: 8/29/2026
Affecting: pac4j >= 0, < 6.5.6
CVE: CVE-2026-82462
CWE: CWE-345 Insufficient Verification of Data Authenticity
CVSS: 6.9
CVSS V4 Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
References: Patch Commit
pac4j Security Advisory for pac4j-core, pac4j-oidc and pac4j-saml
https://github.com/pac4j/pac4j/blob/pac4j-parent-6.5.5/pac4j-oidc/src/main/java/org/pac4j/oidc/credentials/extractor/OidcCredentialsExtractor.java
https://github.com/pac4j/pac4j
Credit: Joshua Rogers (AISLE Research)
Description: pac4j-oidc before 6.5.6 accepts OIDC callbacks carrying only an access token without authorization code or ID token validation. Attackers can substitute access tokens minted for other clients to create authenticated sessions without proper issuer, audience, nonce, or subject verification.

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