How severe is CVE-2023-25581?

No CVSS score has been assigned to CVE-2023-25581 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2023-25581?

CVE-2023-25581 affects the following packages: org.pac4j:pac4j-core (Maven). Ecosystems affected: Maven.

How do I fix CVE-2023-25581?

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 CVE-2023-25581 is resolved across your whole dependency graph.

How do I detect CVE-2023-25581 in my Maven dependencies?

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.

How do I mitigate CVE-2023-25581 if there is no patch (or I can't update yet)?

Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Is CVE-2023-25581 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-25581 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-25581?

CVE-2023-25581 has an EPSS (Exploit Prediction Scoring System) score of 1.9%, placing it in the 80th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-25581?

CVE-2023-25581 is classified as Deserialization of Untrusted Data (CWE-502). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2023-25581 published, and has it been updated?

CVE-2023-25581 was published on October 10, 2024 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2023-25581 — pac4j-core

CVE-2023-25581 is a 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.

Deserialization of untrusted data in InternalAttributeHandler in pac4j

Also known asGHSA-76mw-6p95-x9x5

Published

Oct 10, 2024

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 4, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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 CVE-2023-25581.

EPSS Exploitation Probability

via FIRST.org ↗

1.9%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs80th percentile — riskier than 80% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

Real-World Exposure

1 pkg affected

☕org.pac4j:pac4j-core

Real-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

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.pac4j:pac4j-core`	all versions	4.0.0`org.pac4j:pac4j-core:4.0.0`

Detection & mitigation playbook

Open-source dependency

Detect
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 CVE-2023-25581 is resolved across your whole dependency graph.
Workarounds
Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

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 allo

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