workos authkit-session up to 0.5.0 AuthService.handleCallback state redirect

Summaryinfo

A vulnerability classified as problematic was found in workos authkit-session up to 0.5.0. Affected is the function AuthService.handleCallback. Such manipulation of the argument state leads to redirect. This vulnerability is listed as CVE-2026-42565. The attack may be performed from remote. There is no available exploit. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in workos authkit-session up to 0.5.0 and classified as problematic. Affected by this issue is the function AuthService.handleCallback. The manipulation of the argument state with an unknown input leads to a redirect vulnerability. Using CWE to declare the problem leads to CWE-601. A web application accepts a user-controlled input that specifies a link to an external site, and uses that link in a Redirect. This simplifies phishing attacks. Impacted is integrity. CVE summarizes:

@workos/authkit-session is a toolkit for building WorkOS AuthKit framework integrations. Prior to 0.5.1, an open redirect vulnerability exists in AuthService.handleCallback due to insufficient validation of the returnPathname value derived from the OAuth state parameter. The state parameter is round-tripped through the identity provider (IdP) and can be influenced by an attacker. The handleCallback function decodes and returns returnPathname without enforcing restrictions on origin or scheme. As a result, attacker-controlled values may be returned to the application. If this value is used directly in a redirect, it may cause the user to be redirected to an external, attacker-controlled site. This vulnerability is fixed in 0.5.1.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-42565 since 04/28/2026. 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. The MITRE ATT&CK project declares the attack technique as T1204.001.

Upgrading to version 0.5.1 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch f56e1d6214a93160759e5677b7a3d772b244db39 is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• workos

Name

• authkit-session

Version

• 0.1
• 0.2
• 0.3
• 0.4
• 0.5.0

License

• open-source

Website

• Product: https://github.com/workos/authkit-session/

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