PAC4J has a Cross-Site Request Forgery (CSRF) Vulnerability

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

7.0 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:H/VA:L/SC:N/SI:N/SA:N · score source

EPSS

• CVE-2026-40458: 0.17% estimated exploitation activity in the next 30 days; percentile 5.82 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

PAC4J is vulnerable to Cross-Site Request Forgery (CSRF). A malicious attacker can craft a specially designed website which, when visited by a user, will automatically submit a forged cross-site request with a token whose hash collides with the victim's legitimate CSRF token. Importantly, the attacker does not need to know the victim’s CSRF token or its hash prior to the attack. Collisions in the deterministic String.hashCode() function can be computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent. This issue was fixed in PAC4J versions 5.7.10 and 6.4.1.

Published by the source

17 Apr 2026, 15:31 UTC

Last modified by the source

24 Apr 2026, 20:59 UTC

Source last checked

26 Oct 2026, 16:45 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-xw5c-jc7x-gf75

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# Patch Next advisory brief: CVE-2026-40458

Advisory: PAC4J has a Cross-Site Request Forgery (CSRF) Vulnerability
IDs: CVE-2026-40458, GHSA-xw5c-jc7x-gf75
Record: https://patchnext.com/advisories/cve-2026-40458 (revision 1, source checked 26 Oct 2026, 16:45 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.0)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: org.pac4j:pac4j-core 6.4.1, 5.7.10. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.pac4j:pac4j-core: affected < 5.7.10; >= 6.0.0-RC1, < 6.4.1; fixed in 6.4.1, 5.7.10

## Suggested inspection (read-only)
- Maven org.pac4j:pac4j-core: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on org.pac4j:pac4j-core.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-xw5c-jc7x-gf75 (GitHub-reviewed advisory GHSA-xw5c-jc7x-gf75 lists affected ranges: Maven org.pac4j:pac4j-core >=0 =6.0.0-RC1 <6.4.1)

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