better-auth up to 1.1.19 callbackURL redirect

Summaryinfo

A vulnerability has been found in better-auth up to 1.1.19 and classified as problematic. Impacted is an unknown function. This manipulation of the argument callbackURL causes redirect. The identification of this vulnerability is CVE-2025-27143. It is possible to initiate the attack remotely. There is no exploit available. The affected component should be upgraded.

Detailsinfo

A vulnerability was found in better-auth up to 1.1.19. It has been declared as problematic. Affected by this vulnerability is an unknown part. The manipulation of the argument callbackURL with an unknown input leads to a redirect vulnerability. The CWE definition for the vulnerability is 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. As an impact it is known to affect integrity. The summary by CVE is:

Better Auth is an authentication and authorization library for TypeScript. Prior to version 1.1.21, the application is vulnerable to an open redirect due to improper validation of the callbackURL parameter in the email verification endpoint and any other endpoint that accepts callback url. While the server blocks fully qualified URLs, it incorrectly allows scheme-less URLs. This results in the browser interpreting the URL as a fully qualified URL, leading to unintended redirection. An attacker can exploit this flaw by crafting a malicious verification link and tricking users into clicking it. Upon successful email verification, the user will be automatically redirected to the attacker's website, which can be used for phishing, malware distribution, or stealing sensitive authentication tokens. This CVE is a bypass of the fix for GHSA-8jhw-6pjj-8723/CVE-2024-56734. Version 1.1.21 contains an updated patch.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2025-27143 since 02/19/2025. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1204.001 according to MITRE ATT&CK.

Upgrading to version 1.1.20 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch 24659aefc35a536b95ea4e5347e52c8803910153 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

Name

• better-auth

Version

• 1.1.0
• 1.1.1
• 1.1.2
• 1.1.3
• 1.1.4
• 1.1.5
• 1.1.6
• 1.1.7
• 1.1.8
• 1.1.9
• 1.1.10
• 1.1.11
• 1.1.12
• 1.1.13
• 1.1.14
• 1.1.15
• 1.1.16
• 1.1.17
• 1.1.18
• 1.1.19

License

• open-source

Website

• Product: https://github.com/better-auth/better-auth/

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