GitHub Advisoryadvisory · npm

GHSA-wmjr-v86c-m9jj Better Auth's multi-session sign-out hook allows forged cookies to revoke arbitrary sessions

LOW Published 2025-11-26 Modified 2026-05-08 Official page ↗
Ecosystem
npm
Packages
better-auth
Severity
Low
CVSS vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:L/VI:L/VA:L/SC:L/SI:L/SA:N
Weaknesses
CWE-287, CWE-345
Reviewed
2025-11-26

Affected packages

• npm better-auth: >= 1.3.34, < 1.4.0 → fixed in 1.4.0

Description

Summary A vulnerability was identified in the multi-session plugin for Better Auth, specifically in the /sign-out after-hook. The hook trusts raw multi-session cookies and forwards the extracted values directly to internalAdapter.deleteSessions without verifying the cookie signature. Because cookie values are not validated with getSignedCookie (or any equivalent check), an attacker can supply a forged _multi-* cookie to trigger deletion of arbitrary session tokens.

Related

Weakness · CWE (2)

  • CWE-287 Improper Authentication weakness
  • CWE-345 Insufficient Verification of Data Authenticity weakness

References