Roundcube Webmail 1.6.x between 1.6.14 and 1.6.16,and 1.7.x before 1.7.1 has 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. The issue stems from an insufficient fix for CVE-2026-35540.
https://roundcube.net/news/2026/05/24/security-updates-1.6.16-and-1.7.1
https://github.com/roundcube/roundcubemail/releases/tag/1.7.1
https://github.com/roundcube/roundcubemail/releases/tag/1.6.16
https://github.com/roundcube/roundcubemail/commit/cb3fc9041e91640ba9ba49ee7b2147c176ebf5a1
https://github.com/roundcube/roundcubemail/commit/ab96c88bfd888866ec5e02190b19618db283923a