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Deserialization of Untrusted DataWeakness · CWE-502

CVE-2023-25581

CRITICAL · 9.2 CVSS v4.0 Published 2024-10-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

pac4j-core versions before 4.0.0 contain a Java deserialization vulnerability in the UserProfile class. Attackers can achieve RCE by storing Base64-encoded serialized Java objects prefixed with `{#sb64}` in UserProfile attributes. While a RestrictedObjectInputStream restricts deserialization, it still permits sufficient gadget chains for exploitation.

MitigationUpgrade pac4j to version 4.0.0 or later. No workarounds exist; immediate patching is required given the CRITICAL severity and RCE potential.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
Authentication
X
User interaction
None
Scope
X

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Locate pac4j-core library in your project
    Search for pac4j-core jar files in your application lib/deployments directories, or check your dependency management file (Maven pom.xml, Gradle build.gradle) for the pac4j-core dependency
    Affected if pac4j-core is present in your environment
  2. Determine installed pac4j-core version
    Check the exact version of pac4j-core in your dependency lock file (pom-lock.xml, gradle.lockfile) or by inspecting the jar manifest. For Maven, run: mvn dependency:list | grep pac4j-core
    Affected if The version is lower than 4.0.0 (e.g., 3.x.x, 2.x.x)
  3. Identify if UserProfile deserialization is in use
    Search your codebase for deserialization of UserProfile objects, particularly any code that reads serialized objects from cookies, sessions, or HTTP parameters into UserProfile class attributes. Look for patterns involving ObjectInputStream or similar deserialization mechanisms.
    Affected if Your application deserializes UserProfile objects from untrusted input sources such as HTTP requests, cookies, or session data
  4. Check for {#sb64} prefix handling in code
    Search source code for string patterns containing '{#sb64}' which indicates base64-encoded serialized object handling within pac4j. Review any custom serializers or profile service implementations.
    Affected if Code handles or expects objects prefixed with {#sb64} in serialization contexts
  5. Review RestrictedObjectInputStream configuration
    Inspect your pac4j configuration to see if RestrictedObjectInputStream is in use and which package allowlists are configured. Check for any custom security configuration that may have been added around the deserialization flow.
    Affected if RestrictedObjectInputStream allows deserialization from packages known to contain gadget chains (e.g., org.apache.commons, org.springframework, etc.)

You are affected if pac4j-core version is below 4.0.0 AND your application deserializes UserProfile objects from external input sources using the pac4j serialization mechanism.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade pac4j to version 4.0.0 or later. No workarounds exist; immediate patching is required given the CRITICAL severity and RCE potential.

Recommended fix High confidence

pac4j-core version 4.0.0 or later

  1. Identify all dependencies that include pac4j-core in your project
  2. Locate the pom.xml, build.gradle, or other dependency management files
  3. Find the current version of pac4j-core (likely a version prior to 4.0.0)
  4. Update the pac4j-core dependency to version 4.0.0 or later
  5. Rebuild and test the application to ensure the upgrade does not break existing functionality
Caveat Review the pac4j 4.0.0 release notes and changelog for potential breaking changes, as this is a major version upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation2.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,080
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2023-25581 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data