CVE-2025-71402: Better-Auth

Low severity, CVSS 2.0. EPSS: 0.3% chance of exploitation in the next 30 days.

better-auth versions greater than 1.3.34 and before 1.4.0 contain a vulnerability in the multi-session plugin's /sign-out after-hook, which trusts raw multi-session cookies and forwards extracted values to internalAdapter.deleteSessions without verifying the cookie signature (e.g., via getSignedCookie). An attacker can supply a forged _multi-* cookie to trigger deletion of arbitrary session tokens.

Affected products

• Better-Auth Better-Auth: before 1.4.0 (fixed in 1.4.0)

Published 2026-08-01. Last modified 2026-10-06.