CVE-2025-27143 Information

Description

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.

Reference

https://github.com/better-auth/better-auth/commit/24659aefc35a536b95ea4e5347e52c8803910153 https://github.com/better-auth/better-auth/commit/b381cac7aafd6aa53ef78b6ab771ebfa24643c80 https://github.com/better-auth/better-auth/releases/tag/v1.1.21 https://github.com/better-auth/better-auth/security/advisories/GHSA-8jhw-6pjj-8723 https://github.com/better-auth/better-auth/security/advisories/GHSA-hjpm-7mrm-26w8 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.