pac4j-core affected by a Java deserialization vulnerability

Exploitation

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

CVSS 4.0

9.2 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X · score source

EPSS

• CVE-2023-25581: 1.94% estimated exploitation activity in the next 30 days; percentile 80.09 (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 a security framework for Java. pac4j-core prior to version 4.0.0 is affected by a Java deserialization vulnerability. The vulnerability affects systems that store externally controlled values in attributes of the UserProfile class from pac4j-core. It can be exploited by providing an attribute that contains a serialized Java object with a special prefix {#sb64} and Base64 encoding. This issue may lead to Remote Code Execution (RCE) in the worst case. Although a RestrictedObjectInputStream is in place, that puts some restriction on what classes can be deserialized, it still allows a broad range of java packages and potentially exploitable with different gadget chains. pac4j versions 4.0.0 and greater are not affected by this issue. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Published by the source

11 Oct 2024, 22:16 UTC

Last modified by the source

11 Oct 2024, 22:16 UTC

Source last checked

26 Oct 2026, 16:31 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-76mw-6p95-x9x5

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# Patch Next advisory brief: CVE-2023-25581

Advisory: pac4j-core affected by a Java deserialization vulnerability
IDs: CVE-2023-25581, GHSA-76mw-6p95-x9x5
Record: https://patchnext.com/advisories/cve-2023-25581 (revision 1, source checked 26 Oct 2026, 16:31 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.2)
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 4.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Maven org.pac4j:pac4j-core: affected < 4.0.0; fixed in 4.0.0

## 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-76mw-6p95-x9x5 (GitHub-reviewed advisory GHSA-76mw-6p95-x9x5 lists affected ranges: Maven org.pac4j:pac4j-core >=0 <4.0.0)

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