Vulnerability · Published Aug 1, 2026 · Assigned by VulnCheck

CVE-2026-67336better-auth before 1.6.11 Insecure Cryptographic Defaults via oidcProvider

High 8.7

In plain English

A high-severity broken cryptography 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 0.2% (higher than 15% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.7High

Exploit odds (30 days)0.2%top 85.3% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

better-auth versions before 1.6.11 contain insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and accept plain PKCE by default. Attackers can exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes when PKCE plain is used instead of the required S256 method.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
npm	better-auth	1.6.11	GHSA-9h47-pqcx-hjr4

Affected products (as reported)

Vendor	Product	Versions
better-auth	better-auth	0 – before 1.6.11

Weakness: CWE-327 · Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:N

References

GitHub Security Advisory (GHSA-9h47-pqcx-hjr4) vendor-advisory
VulnCheck Advisory: better-auth before 1.6.11 Insecure Cryptographic Defaults via oidcProvider third-party-advisory