CVE-2026-67336 · Symaro Security Advisory

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.

Severity (CVSS)

Base score	9.4
Severity	Critical
Version	CVSS 4.0
Vector	CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N
Provided by	CNA

Weaknesses

CWE-327 — Use of a Broken or Risky Cryptographic Algorithm

Affected products

Vendor	Product	Versions
better-auth	better-auth	0 to <1.6.11; 1.6.11

References

https://github.com/better-auth/better-auth/security/advisories/GHSA-9h47-pqcx-hjr4 (vendor-advisory)
https://www.vulncheck.com/advisories/better-auth-before-insecure-cryptographic-defaults-via-oidcprovider (third-party-advisory)

Authoritative sources

This page is a snapshot. For the latest enrichment and updates, view the record on CVE.org or the NVD.

Generated from the official CVE List on 02 Aug 2026 07:05 UTC.