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.
{
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2025/71xxx/CVE-2025-71402.json",
"cwe_ids": [
"CWE-347"
],
"cna_assigner": "VulnCheck"
}