What’s Vulnerable › Vulnerabilities

CVE-2025-71402: better-auth before 1.4.0 Session Revocation via Forged Cookie

• Severity: low (CVSS 2.0 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-01 · updated 2026-10-06
• Weakness: CWE-347

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.

Affected products

• better-auth: before 1.4.0 — fixed in 1.4.0

How to fix

Upgrade to a fixed version: better-auth 1.4.0. Check the vendor advisory for mitigations.

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

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