CVE-2026-35540: Roundcube Webmail

Medium severity, CVSS 6.5. EPSS: 0.4% chance of exploitation in the next 30 days.

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.

Affected products

• Roundcube Webmail: from 1.6.0, before 1.6.14 (fixed in 1.6.14)

Published 2026-04-03. Last modified 2026-07-24.