better-auth up to 1.3.34 Multi-Session Plugin internalAdapter.deleteSessions _multi-* input validation

Summaryinfo

A vulnerability was found in better-auth up to 1.3.34. It has been declared as critical. Impacted is the function internalAdapter.deleteSessions of the component Multi-Session Plugin. Executing a manipulation of the argument _multi-* can lead to input validation. This vulnerability appears as CVE-2025-71402. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability has been found in better-auth up to 1.3.34 and classified as critical. This vulnerability affects the function internalAdapter.deleteSessions of the component Multi-Session Plugin. The manipulation of the argument _multi-* with an unknown input leads to a input validation vulnerability. The CWE definition for the vulnerability is CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability was named CVE-2025-71402 since 07/18/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. Technical details are known, but there is no available exploit.

Upgrading to version 1.4.0 eliminates this vulnerability.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

Name

• better-auth

Version

• 1.3.0
• 1.3.1
• 1.3.2
• 1.3.3
• 1.3.4
• 1.3.5
• 1.3.6
• 1.3.7
• 1.3.8
• 1.3.9
• 1.3.10
• 1.3.11
• 1.3.12
• 1.3.13
• 1.3.14
• 1.3.15
• 1.3.16
• 1.3.17
• 1.3.18
• 1.3.19
• 1.3.20
• 1.3.21
• 1.3.22
• 1.3.23
• 1.3.24
• 1.3.25
• 1.3.26
• 1.3.27
• 1.3.28
• 1.3.29
• 1.3.30
• 1.3.31
• 1.3.32
• 1.3.33
• 1.3.34

Website

• Product: https://github.com/better-auth/better-auth/

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