Improper Neutralization of Special Elements in Output Used by a Downstream Component in Roundcube Webmail - #VU156148
Published: October 19, 2026
Vulnerability identifier: #VU156148
CSH Severity: Medium
CVSS v4: 5.1 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-74
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to apply message-supplied CSS outside its intended scope and potentially manipulate the surrounding interface.
The vulnerability exists due to insufficient CSS scoping in HTML message rendering when processing CSS at-rules. A remote attacker can supply an HTML message containing crafted at-rules to escape the intended style boundary and affect the presentation of content outside the message.
Affected software
Roundcube Webmail
Remediation
Install security update from vendor's website.
Roundcube Webmail - addressed in versions 1.6.20, 1.7.5