CVE-2026-67336 better-auth before 1.6.11 Insecure Cryptographic Defaults via oidcProvider
Attackers can bypass authentication or intercept codes due to insecure cryptographic defaults in the oidcProvider plugin.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-67336?
CVE-2026-67336 is a critical vulnerability in better-auth, published on 1 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-327
Which versions are affected by CVE-2026-67336?
2 open source packages ship an affected version, including better-auth.
| Package | Affected | Fixed in |
|---|---|---|
better-auth npm | All versions | 1.6.11 |
better-auth npm | All versions | 1.6.11 |
How do I fix CVE-2026-67336?
Upgrade better-auth to 1.6.11 or later.
Is CVE-2026-67336 being exploited?
There is no known exploitation of CVE-2026-67336 in the wild and no public exploit code.
Sources
Also known as GHSA-9h47-pqcx-hjr4, GHSA-mw34-3w2r-wp9p.