---
cve: "CVE-2026-35540"
severity: "MEDIUM"
cvss: 5.4
epss: "0.4%"
vendor: "Roundcube"
kev: false
exploited: false
published: "2026-04-03 05:16:22"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-10-28T21:30:23+01:00"
---

# CVE-2026-35540

> 5.4 MEDIUM · 🧪 PoC

## Beschreibung

An issue was discovered in Roundcube Webmail 1.6.0 before 1.6.14. Insufficient Cascading Style Sheets (CSS) sanitization in HTML e-mail messages may lead to SSRF or Information Disclosure, e.g., if stylesheet links point to local network hosts.

## CNA-Record (Kanon, cvelistV5)

- CNA: **mitre**
- State: PUBLISHED
- Stand: 2026-04-03 12:52:38
- CNA-CVSS: **5.4** (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **none**
  - Automatable: **no**
  - Technical Impact: **partial**

## CVSS-Vektor

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

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

## Schwachstellen-Klasse

- **CWE-669** — Incorrect Resource Transfer Between Spheres
  The product does not properly transfer a resource/behavior to another sphere, or improperly imports a resource/behavior from another sphere, in a manner that provides unintended control over that resource.

## Patch verfügbar (OSV)

- 27ec6cc9cb25e1ef8b4d4ef39ce76d619caa6870 (Commit)
- 579b68eff90650a5c782e153debd66c765648942 (Commit)

## BSI-Hinweise (deutsch)

- [Roundcube: Mehrere Schwachstellen](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-0789) — _BSI-Einstufung: mittel_
  Ein Angreifer kann mehrere Schwachstellen in Roundcube ausnutzen, um Dateien zu manipulieren, um Sicherheitsvorkehrungen zu umgehen, um einen Cross-Site Scripting Angriff durchzuführen, und um Informationen offenzulegen.

## Referenzen

- <https://roundcube.net/news/2026/03/18/security-updates-1.7-rc5-1.6.14-1.5.14>
- <https://github.com/roundcube/roundcubemail/releases/tag/1.7-rc5>
- <https://github.com/roundcube/roundcubemail/commit/579b68eff90650a5c782e153debd66c765648942>
- <https://github.com/roundcube/roundcubemail/releases/tag/1.6.14>
- <https://github.com/roundcube/roundcubemail/commit/27ec6cc9cb25e1ef8b4d4ef39ce76d619caa6870>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-35540/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_