CVE-2025-71402

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.

Score

CVSS 4.0 2.0 Low

Status

Deferred - disclosure@vulncheck.com

Published

2026-08-01

Last modified

2026-10-06

Weaknesses

CWE-347

Affected products

• Better-auth/oauth-provider (Better-auth)

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