Better Auth
CVE-2025-27143
MEDIUM
Vulnerability Assessment
| Weakness |
CWE
OWASP Top 10:2025
A01:2025 - Broken Access Control
ASVS 5.0
V3 - Web Frontend Security Redirect URL validation
MITRE ATT&CK
1 technique across 1 tactic: Initial Access The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up. |
| Impact | CVSS score of 6.9 (MEDIUM). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. EPSS exploitation probability: 0.15%. |
| Exploit ScenarioDerived | A remote attacker could redirect users to malicious websites via URL manipulation by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability. |
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Alert meAnalysisAIv1 – Mar 28, 2026
Better Auth is an authentication and authorization library for TypeScript. Rated medium severity (CVSS 6.9), this vulnerability is remotely exploitable, no authentication required, low attack complexity. This Open Redirect vulnerability could allow attackers to redirect users to malicious websites via URL manipulation.
RemediationAI
A vendor patch is available. Apply the latest security update as soon as possible. Validate redirect destinations against an allowlist, avoid using user input in redirect URLs.
Affected Packages
Source: OSV (Open Source Vulnerabilities)
Affects your stack
Affects 1 package in npm
Checking this CVE against your own stacks and servers is part of the Basic plan and up.
Technical ContextAI · show details
This vulnerability is classified as Open Redirect (CWE-601), which allows attackers to redirect users to malicious websites via URL manipulation. 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. Affected products include: Better-Auth Better Auth. Version information: version 1.1.21.
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- Exploit and PoC references, threat intelligence from 22 sources
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Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
Lifecycle Timeline
2DescriptionGitHub Advisory
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.
Executive ViewAI
Organizations using Better Auth should be aware of notable risk from CVE-2025-27143 rated CVSS 6.9. Exploitation could compromise the security of affected deployments. A patch is available and should be applied during regular vulnerability management.
Apply vendor patch. If patching is delayed: restrict network access and enable monitoring.
Threat Intelligence Overview
NVD
CVE.org
EPSS
GitHub
How this decision was reached
The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.
What every action level means
SSVC AssessmentENISA
Priority Score
Affected Products (CPE)GitHub Advisory
More in Better Auth
View allBetter Auth is an authentication library for TypeScript. Rated high severity (CVSS 7.9), this vulnerability is remotely
Authorization bypass in the @better-auth/oauth-provider plugin for Better Auth (versions >= 1.4.8-beta.7 and < 1.6.5, pl
Privilege-escalating account takeover in the @better-auth/scim plugin (versions 1.4.0-beta.27 through 1.6.21 and 1.7.0-b
Authentication bypass in Better Auth before 1.6.11 stems from insecure cryptographic defaults in the legacy oidcProvider
Denial of service in Better Auth (npm) before 1.4.2 lets an unauthenticated remote attacker poison the router's base pat
Unauthenticated OAuth state values can be redeemed as Magic Link tokens in Better Auth 1.4.0-beta.18 through 1.7.6, lett
Authentication bypass in Better Auth's OAuth Proxy plugin (versions 1.5.0-beta.12 through 1.7.6) lets unauthenticated re
Path normalization bypass in Better Auth before v1.4.5 allows unauthenticated remote attackers to circumvent `disabledPa
Authorization bypass in @better-auth/scim versions 1.5.0 through 1.7.0-beta.3 allows any authenticated user to fully tak
Pre-account hijacking in better-auth (npm) allows a remote attacker to gain persistent, password-based access to any vic
Multiple authentication bypass vulnerabilities in @better-auth/sso before version 1.6.21 enable low-privileged attackers
Two domain-ownership authentication bypass flaws in @better-auth/sso allow authenticated organization owners to compromi
Exploit-DB