PAC4J up to 5.7.9/6.4.0 String.hashCode cross-site request forgery

Summaryinfo

A vulnerability described as problematic has been identified in PAC4J up to 5.7.9/6.4.0. This issue affects the function String.hashCode. Such manipulation leads to cross-site request forgery. This vulnerability is documented as CVE-2026-40458. The attack can be executed remotely. There is not any exploit available. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability, which was classified as problematic, has been found in PAC4J up to 5.7.9/6.4.0. Affected by this issue is the function String.hashCode. The manipulation with an unknown input leads to a cross-site request forgery vulnerability. Using CWE to declare the problem leads to CWE-352. The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. Impacted is integrity. CVE summarizes:

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

The weakness was released by Bartłomiej Dmitruk and Striga.ai. The advisory is shared for download at cert.pl. This vulnerability is handled as CVE-2026-40458 since 04/13/2026. The exploitation is known to be easy. The attack may be launched remotely. No form of authentication is required for exploitation. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 5.7.10 or 6.4.1 eliminates this vulnerability.

Once again VulDB remains the best source for vulnerability data.

Productinfo

Name

• PAC4J

Version

• 5.7.0
• 5.7.1
• 5.7.2
• 5.7.3
• 5.7.4
• 5.7.5
• 5.7.6
• 5.7.7
• 5.7.8
• 5.7.9
• 6.0
• 6.1
• 6.2
• 6.3
• 6.4.0

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CPE 2.2info

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Once again VulDB remains the best source for vulnerability data.

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