PT-2026-44369 · Roundcube · Webmail

Guillaume Meunier · Published 2026-05-28 · Updated 2026-05-28 · CVE-2026-9818

Mitre

CVSS v3.1

4.7

Medium

Base vector

AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N

Roundcube's HTML sanitization path for message rendering allows loopback, localhost, RFC1918, link-local, and ULA URLs even when remote content loading is disabled. A remote attacker can send an HTML email that causes the victim's browser to issue requests to local or private-network services simply by opening the message preview.

Fix

Incomplete List of Disallowed Inputs

Weakness Enumeration

CWE-184

Related Identifiers

CVE-2026-9818

Affected Products

Webmail

References · 6

• https://github.com/roundcube/roundcubemail/commit/faf867432f51ebbe100382a70a9e3c042415ee1b · Patch
• https://github.com/roundcube/roundcubemail/releases/tag/1.6.16 · Patch
• https://github.com/roundcube/roundcubemail/commit/7b52353653a67e6073b97d70eb94047132b78556 · Patch
• https://github.com/roundcube/roundcubemail/releases/tag/1.7.1 · Patch
• https://nvd.nist.gov/vuln/detail/CVE-2026-9818 · Security Note
• https://advisories.orangecyberdefense.com/advisories/163 · Note