CVE-2026-67337: better-auth before 1.4.9 Two-Factor Authentication Bypass via session.cookieCache

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-01 · updated 2026-09-08
Weakness: CWE-288

Description

better-auth versions before 1.4.9 contain a two-factor authentication bypass vulnerability when session.cookieCache is enabled. Attackers with valid primary credentials can access authenticated routes without completing second-factor verification by exploiting premature session caching.

Affected products

better-auth: before 1.4.9 — fixed in 1.4.9

How to fix

Upgrade to a fixed version: better-auth 1.4.9. Check the vendor advisory for mitigations.

References

https://github.com/better-auth/better-auth/security/advisories/GHSA-xg6x-h9c9-2m83
https://www.vulncheck.com/advisories/better-auth-before-two-factor-authentication-bypass-via-session-cookiecache

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