Medium · published October 22, 2026
Roundcube Webmail before 1.6.20 and 1.7.x before 1.7.5 is affected by a mail header injection vulnerability. rcmail_sendmail stripped newline characters only from the Subject and Organization headers, leaving other header values taken from request parameters unsanitized, so a remote authenticated attacker could inject arbitrary headers into an outgoing message via the References, In-Reply-To, Message-ID and From parameters. Upstream fixed this in the commit “Fix mail header injection via References/In-Reply-To/Message-ID/From parameters”, which normalizes whitespace in every string header value.