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9.1

Better Auth lets attackers log in as other users

CVE-2026-110862 · published 6 days ago
Summary

The Better Auth library (versions from 1.4.0‑beta.18 up to 1.7.6) can be tricked into accepting a reused login token, letting anyone sign in as another person or create a fake verified account. This means an unauthenticated attacker could gain access to user data or perform actions on behalf of a victim. Update to version 1.7.7 or later, or apply vendor‑provided patches, to stop the misuse of these tokens.

What to do
  • Update better-auth better-auth to version 1.7.7 or later.
Affected software
VendorProductAffected versions
better-auth better-auth < 1.7.7
Original advisory text
Better Auth 1.4.0-beta.18 before 1.7.7 Authentication Bypass via Magic Link
Better Auth from 1.4.0-beta.18 before 1.7.7 contains an authentication bypass vulnerability that allows unauthenticated attackers to sign in as other users by reusing OAuth state values as Magic Link tokens. Attackers can start an OAuth sign-in with a victim's email and submit the returned state to Magic Link verification, gaining sessions or creating falsely email-verified accounts.
References
Fix within
Internet-facing 3 days
Internal 60 days
  • Not known to be exploited
  • Can be exploited automatically
  • Gives an attacker full control
Severity
9.1 Critical
Exploitation
<1% chance of attack within 30 days
Type
CWE-287Improper Authentication
Timeline
Published14 Oct 2026
Updated19 Oct 2026
First seen14 Oct 2026
Sources
CVE-2026-110862 · NVD
CVE-2026-110862 · MITRE
CVE-2026-110862 · OSV
GHSA-965c-763c-88jm · GHSA
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