Is CVE-2025-71402 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2025-71402 being exploited in the wild.

How severe is CVE-2025-71402?

Medium severity, with a CVSS score of 4, published 1 August 2026.

Which products and versions are affected?

better-auth (npm) SEMVER:introduced=1.3.34,fixed=1.4.0.

Is there a fix for CVE-2025-71402?

Yes. better-auth (npm): upgrade to 1.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2025-71402 attacked?

It is attacked over the network.

Am I affected by CVE-2025-71402?

Check whether you run better-auth (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2025-71402: Better Auth multi-session cookie signature bypass

CVE-2025-71402 · Severity: medium · CVSS 4 · Published 2026-08-01

Better Auth is an authentication library used by web applications to manage user sessions. The library's multi-session sign-out feature fails to validate cookie signatures, allowing an attacker to forge session cookies and force the sign-out of other users' sessions. This could disrupt service for legitimate users or be chained with other attacks to facilitate account compromise.

Technologies: better-auth (npm). Vendors: npm.

Quick answers

Is CVE-2025-71402 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2025-71402 being exploited in the wild.
How severe is CVE-2025-71402?: Medium severity, with a CVSS score of 4, published 1 August 2026.
Which products and versions are affected?: better-auth (npm) SEMVER:introduced=1.3.34,fixed=1.4.0.
Is there a fix for CVE-2025-71402?: Yes. better-auth (npm): upgrade to 1.4.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-71402 attacked?: It is attacked over the network.
Am I affected by CVE-2025-71402?: Check whether you run better-auth (npm) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

better-auth (npm): upgrade to 1.4.0 or later
```
npm install better-auth@1.4.0
```

Technical details

The vulnerability is an authentication bypass in the multi-session plugin's /sign-out after-hook. The hook extracts values from raw _multi-* cookies and passes them directly to internalAdapter.deleteSessions without validating the cookie signature using getSignedCookie or equivalent verification. An attacker on the network can craft forged cookies to trigger deletion of arbitrary session tokens. The issue affects Better Auth versions 1.3.34 through 1.3.x and is fixed in version 1.4.0. The attack requires network access and high privileges but only passive user interaction, resulting in low confidentiality, integrity, and availability impact according to CVSS v4.

Affected products

Better Auth better-auth 1.3.34 through 1.3.x, fixed in 1.4.0

Identifiers

CVE-2025-71402
GHSA-wmjr-v86c-m9jj

Timeline

2025-11-26: disclosed
2025-11-26: patched: Version 1.4.0 available as of disclosure date

References

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