[RCD] Security updates 1.7.3 and 1.6.18 released

Note: Message originally sent on 2026-08-09, but not delivered because of the mailing list issues.

We just published security updates to the 1.7 and 1.6 LTS versions of Roundcube Webmail. They both contain fixes for recently reported security vulnerabilities.

Security fixes:

• Add basic validation for content proxied by the css proxy
• Fix SSRF bypass via specific local address URLs using 100.64.0.0/10

and fe80::/10 nets, reported by Dmytro Ivanenko

• Fix SSRF filter bypass via various forms of nip.io/sslip.io hostnames

evading is_local_url() check, reported by Milan Hoppe

• Fix remote content blocking bypass via unclosed url() in a FuncIRI

attribute, reported by Milan Hoppe

• Fix LDAP filter injection via unescaped %u/%fu/%d substitution into

the search_filter, reported by Milan Hoppe

• Fix arbitrary Sieve script injection via a filter rule name bypassing

managesieve_disabled_actions, reported by Milan Hoppe

• Fix RCE via cmd_learn driver of markasjunk plugin, reported by nept1337
• Fix IMAP command injection via mail search and LITERAL+ byte-count

desynchronization, reported by Zach Hanley of Horizon3.ai

• Fix password's modoboa driver leak of an authentication token to a

user-controlled host, reported by meifukun

• Fix stored XSS in "Add to address book" action, reported by Paulos

Yibelo from pwn.ai

• Fix HTML/CSS sanitization bypass via SVG animate by attribute,

reported by vectrain

See the full changelogs in the release notes on the Github download pages for the updated versions.

https://github.com/roundcube/roundcubemail/releases/tag/1.7.3 https://github.com/roundcube/roundcubemail/releases/tag/1.6.18

We strongly recommend to update all productive installations of Roundcube 1.6.x and 1.7.x with this new versions.