CVE-2025-71402

Description

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.

References

• https://github.com/better-auth/better-auth/security/advisories/GHSA-wmjr-v86c-m9jj
• https://www.vulncheck.com/advisories/better-auth-before-session-revocation-via-forged-cookie