Vulnerability · Published Aug 1, 2026 · Assigned by VulnCheck

CVE-2026-67335better-auth before 1.6.2 OAuth State Validation Bypass

Medium 5.3

In plain English

A medium-severity improper authentication in better-auth from better-auth. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium

Exploit odds (30 days)0.3%top 79.1% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

better-auth versions before 1.6.2 fail to validate the OAuth state parameter against the stored nonce when using cookie-backed state storage without PKCE. Attackers can forge the state parameter and supply an attacker-controlled authorization code to create authenticated sessions bound to the attacker's external identity or persistently link attacker accounts to victim profiles.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	better-auth	1.6.2	GHSA-wxw3-q3m9-c3jr

Affected products (as reported)

Vendor	Product	Versions
better-auth	better-auth	0 – before 1.6.2

Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:N/I:H/A:N

References

GitHub Security Advisory (GHSA-wxw3-q3m9-c3jr) vendor-advisory
VulnCheck Advisory: better-auth before 1.6.2 OAuth State Validation Bypass third-party-advisory