GHSA-76mw-6p95-x9x5 — pac4j-core
CRITICALGHSA-76mw-6p95-x9x5 is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in org.pac4j:pac4j-core. A fix is available for org.pac4j:pac4j-core — see the affected versions and patch details below.
pac4j-core affected by a Java deserialization vulnerability
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for GHSA-76mw-6p95-x9x5.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
GHSA-76mw-6p95-x9x5 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
org.pac4j:pac4j-coreReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
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.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.pac4j:pac4j-core | all versions | 4.0.0org.pac4j:pac4j-core:4.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.pac4j:pac4j-core, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update org.pac4j:pac4j-core to 4.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-76mw-6p95-x9x5 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-76mw-6p95-x9x5 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-76mw-6p95-x9x5. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-76mw-6p95-x9x5 in your dependencies?
O3 Security finds GHSA-76mw-6p95-x9x5 across Maven dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.