Better Auth's multi-session sign-out hook allows forged cookies to revoke arbitrary sessions
Priority LOW 38CWE-287Published · Updated
Key facts
- Attack vector
- —
- Privileges required
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- User interaction
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- Attack complexity
- —
- Impact type
- Security bypass
- Confidentiality · integrity · availability
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- Fix status
- Fixed
No CVSS vector from any source. Fix status from GitHub. Impact type from CWE-287.
Summary
### Summary A vulnerability was identified in the multi-session plugin for Better Auth, specifically in the /sign-out after-hook. The hook trusts raw multi-session cookies and forwards the extracted values directly to internalAdapter.deleteSessions without verifying the cookie signature. Because cookie values are not validated with getSignedCookie (or any equivalent check), an attacker can supply a forged _multi-* cookie to trigger deletion of arbitrary session tokens.
Why it matters now
Fix Fixed better-auth (npm): 1.4.0
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | better-auth (npm) | 1.3.34 to before 1.4.0 | 1.4.0 | Patch available | GHSA-wmjr-v86c-m9jj |
- better-auth (npm) Vendor— Affected 1.3.34 to before 1.4.0 Fixed in 1.4.0 Patch available GHSA-wmjr-v86c-m9jj
Remediation
- Fix · GHSA-wmjr-v86c-m9jj better-auth (npm) Fixed in 1.4.0 Advisory →
Timeline
- 2026-10-03 Threatist record created from GHSA-wmjr-v86c-m9jj
References
Sources
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences