GHSA-wmjr-v86c-m9jj

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

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.

Affected packages

References

• https://github.com/better-auth/better-auth/security/advisories/GHSA-wmjr-v86c-m9jj WEB
• https://github.com/better-auth/better-auth/commit/cfc453a2a6eb02951f9a0a7c944064936e73eee8 WEB
• https://github.com/better-auth/better-auth PACKAGE
• https://github.com/better-auth/better-auth/releases/tag/v1.4.0 WEB

Sources