What’s Vulnerable › Vulnerabilities

CVE-2026-82462: pac4j-oidc before 6.5.6 Authentication Bypass via Access Token Substitution

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-29 · updated 2026-09-10
• Weakness: CWE-345

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.

Affected products

• pac4j: before 6.5.6 — fixed in 6.5.6

How to fix

Upgrade to a fixed version: pac4j 6.5.6. Check the vendor advisory for mitigations.

References

• https://github.com/pac4j/pac4j
• 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/commit/2270c3ff70e93cc43831e75702acd5135531237e
• https://www.pac4j.org/blog/security-advisory-pac4j-core-oidc-saml.html
• https://www.vulncheck.com/advisories/pac4j-oidc-before-6.5.6-authentication-bypass-via-access-token-substitution

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