VulnerabilityAnalyzed

CVE-2025-27143

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.

MEDIUM 6.9EPSS 0.34%

Does this matter?

Lower severity and a low EPSS score (0.34%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 4.0: 6.9 MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/M
EPSS: 0.34% probability · 28th percentile
CISA KEV: Not listed
Weakness: CWE-601
Affected: better-auth/better auth
Source: security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.