Is CVE-2026-67336 being exploited?

No public exploit is currently tracked.

How severe is CVE-2026-67336?

CVE-2026-67336 has a CVSS v3 severity of HIGH (8.7).

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CVE-2026-67336

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.