# pac4j-core affected by a Java deserialization vulnerability

Advisory record · `GHSA-76mw-6p95-x9x5`

- **Identifiers:** `GHSA-76mw-6p95-x9x5` · `CVE-2023-25581`
- **State:** Confirmed
- **Severity:** CVSS 9.2 Critical
- **Critical:** Yes: CVSS 9+
- **Weakness (CWE):** [CWE-502](https://cwe.mitre.org/data/definitions/502.html)
- **Tags:** [Insecure deserialization](https://agentprime.io/advisories/tag/deserialization.md)
- **Published:** 11 Oct 2024
- **Updated:** 14 Oct 2024
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 11 Oct 2024, 22:16 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Critical

Critical, because:

- CVSS score 9.2: 9.0 or more.

How we decide what’s critical: <https://agentprime.io/advisories/critical.md>

## Affected packages

- `org.pac4j:pac4j-core` (Maven): affected `<4.0.0`; fixed in `4.0.0`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> pac4j-core versions prior to 4.0.0 are affected by a Java deserialization vulnerability. Systems that store externally controlled values in UserProfile attributes are at risk, since an attacker can supply a specially prefixed, Base64-encoded serialized Java object that may lead to remote code execution. Upgrade to pac4j-core 4.0.0 or later; the source lists no workarounds.

Written 8 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 9.2 Critical, CVSS 4.0: `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`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.019, the 80th percentile, on 14 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 15:13 UTC: First seen by agentprime
- 31 Oct 2026, 15:13 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-76mw-6p95-x9x5)

## Sources

- [GitHub Advisory Database: GHSA-76mw-6p95-x9x5](https://github.com/advisories/GHSA-76mw-6p95-x9x5)
- [OSV: GHSA-76mw-6p95-x9x5](https://osv.dev/vulnerability/GHSA-76mw-6p95-x9x5)
- <https://nvd.nist.gov/vuln/detail/CVE-2023-25581>
- <https://github.com/frohoff/ysoserial>
- <https://github.com/pac4j/pac4j>
- <https://github.com/pac4j/pac4j/blob/5834aeb22ad3a4369dfa572be60d7b20f5784a8f/pac4j-core/src/main/java/org/pac4j/core/profile/InternalAttributeHandler.java#L95>
- <https://portswigger.net/web-security/deserialization>
- <https://securitylab.github.com/advisories>
- <https://securitylab.github.com/advisories/GHSL-2022-085_pac4j>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-76mw-6p95-x9x5>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-76mw-6p95-x9x5/>. Everything for agents: <https://agentprime.io/llms.txt>.