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Pac4jApplication

CVE-2026-40458

MEDIUM · 6.5 CVSS v3.1 Published 2026-04-17
Fix available
A fix is available. Upgrade to 5.7.10 / 6.4.1 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

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 vulnerable to Cross-Site Request Forgery (CSRF). A malicious attacker can craft a specially designed website which, when visited by a user, will automatically submit a forged cross-site request with a token whose hash collides with the victim's legitimate CSRF token. Importantly, the attacker does not need to know the victim’s CSRF token or its hash prior to the attack. Collisions in the deterministic String.hashCode() function can be computed directly, reducing the effective token's security space to 32 bits. This bypasses CSRF protection, allowing profile updates, password changes, account linking, and any other state-changing operations to be performed without the victim's consent. This issue was fixed in PAC4J versions 5.7.10 and 6.4.1

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 CSRF protection relies on token hashing using Java's deterministic String.hashCode(), which has predictable collisions. Attackers can pre-compute hash collisions that will match any victim's legitimate token hash, reducing effective token security to 32 bits and enabling forged CSRF requests for state-changing operations.

MitigationUpgrade PAC4J to version 5.7.10 or 6.4.1 which implements a proper CSRF token generation mechanism that is not vulnerable to hash collision attacks.

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

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Pac4jApplication
Affected:>= 5.0.0, < 5.7.10> 6.0.0, < 6.4.1

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
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N

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. Determine installed Pac4j version
    Inspect your project's dependency management file (Maven pom.xml, Gradle build.gradle) or list all JAR files in the classpath and check the pac4j-core or pac4j-* library version
    Affected if The version is 5.0.0 or higher but below 5.7.10, OR higher than 6.0.0 but below 6.4.1
  2. Verify CSRF protection is in use
    Search configuration files or code for Pac4j security configuration; look for CsrfTokenGenerator, DefaultCsrfToken, or any CSRF-related bean definitions using Pac4j classes
    Affected if The application uses Pac4j's built-in CSRF token generation mechanism for protecting state-changing endpoints
  3. Confirm token-based state-changing endpoints exist
    Review your application's REST or web endpoints; identify POST, PUT, DELETE, or PATCH handlers that perform state changes and rely on Pac4j CSRF validation
    Affected if The application has state-changing operations protected by Pac4j CSRF tokens generated by the vulnerable version
  4. Inspect the CSRF token generator implementation
    In your codebase, locate the CsrfTokenGenerator bean configuration; if using the default generator without custom salt or secure random implementation, it likely relies on String.hashCode()
    Affected if The CSRF token generator uses the default Pac4j implementation that hashes tokens using Java's String.hashCode() method

You are affected if your application uses Pac4j versions 5.0.0-5.7.9 or 6.0.1-6.4.0 with default CSRF token generation for state-changing operations.

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
Upgrade available Upgrade to 5.7.10 / 6.4.1 or later
Fixed in 5.7.106.4.1
Interim mitigation

Upgrade PAC4J to version 5.7.10 or 6.4.1 which implements a proper CSRF token generation mechanism that is not vulnerable to hash collision attacks.

Recommended fix High confidence

pac4j 5.7.10 (for v5.x users) or pac4j 6.4.1 (for v6.x users)

  1. 1. Identify the current pac4j version in your project (check pom.xml, build.gradle, or similar dependency file)
  2. 2. If using pac4j v5.x (5.0.0 to 5.7.9), update the version to 5.7.10 in your dependency management
  3. 3. If using pac4j v6.x (6.0.0 to 6.4.0), update the version to 6.4.1 in your dependency management
  4. 4. Run your build tool to fetch the updated dependency (e.g., mvn clean install for Maven, gradle build for Gradle)
  5. 5. Rebuild and redeploy your application
  6. 6. Verify CSRF protection is working correctly in your environment

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

Fix this in Pac4j Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2026-40458 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