Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a mail header injection vulnerability when a message is forwarded as an attachment. The subject of the forwarded message was used verbatim to generate the attachment name, so a received message whose subject contains CRLF sequences could inject arbitrary MIME part headers into the outgoing message. Upstream fixed this in the commit “Fix mail header injection via subject of a message forwarded as attachment”, which collapses whitespace in the generated name.
https://roundcube.net/news/2026/10/19/security-updates-1.6.20-and-1.7.5
https://github.com/roundcube/roundcubemail/releases/tag/1.7.5
https://github.com/roundcube/roundcubemail/releases/tag/1.6.20
https://github.com/roundcube/roundcubemail/commit/c325953a251d0132f1909569b3eac0b974095dd4
https://github.com/roundcube/roundcubemail/commit/4c3291ce9df9e1d3b45330d0854d65cd8efbeee9