---
cve: "CVE-2026-55674"
severity: "CRITICAL"
cvss: 9.3
epss: "34%"
vendor: "discourse"
kev: false
exploited: false
published: "2026-08-17 16:16:58"
tags: [cve, security, critical]
source: tsecurity.de CVE-Dossier
exported: "2026-09-07T23:30:02+02:00"
---

# CVE-2026-55674

> 9.3 CRITICAL · 🧪 PoC

## Beschreibung

Discourse is an open-source discussion platform. Prior to 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0, an unauthenticated attacker could send a single request with a crafted color_scheme_id (or dark_scheme_id) cookie to inject arbitrary HTML into a Discourse page. Because the cookie value was rendered into a color scheme tag without escaping, the attacker could break out of the attribute and inject a tag that bypassed Discourse's nonce-based Content Security Policy, resulting in arbitrary JavaScript execution in visitors' browsers. This issue is fixed in versions 2026.1.6, 2026.5.2, 2026.6.1, and 2026.7.0.

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Erforderlich | good |
| S Scope | Verändert | bad |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Keine | good |

## Patch verfügbar (OSV)

- 94190ccb5176eb4ab1f2b509fcecc3fc682dadae (Commit)
- 3a87be49d621faddf5cea3f6a090adc9b7cbb7e8 (Commit)

## Referenzen

- <https://github.com/discourse/discourse/security/advisories/GHSA-qx4v-rg4v-pm2g>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-55674) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_