---
cve: "CVE-2026-67336"
severity: "CRITICAL"
cvss: 9.4
epss: "16%"
vendor: "better-auth"
kev: false
exploited: false
published: "2026-08-01 13:17:04"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-14T14:44:12+02:00"
---

# CVE-2026-67336

> 9.4 CRITICAL · 🧪 PoC

## Beschreibung

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.

## CVSS-Vektor

```
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
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Patch verfügbar (OSV)

- f41514ef07cfafc5dbf463bd1500aee6575d88a7 (Commit)

## Referenzen

- <https://github.com/better-auth/better-auth/security/advisories/GHSA-9h47-pqcx-hjr4>
- <https://www.vulncheck.com/advisories/better-auth-before-insecure-cryptographic-defaults-via-oidcprovider>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-67336) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_