Cross-site scripting in Roundcube Webmail - CVE-2026-54432
Published: July 5, 2026
Vulnerability identifier: #VU136903
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:A/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U/U:Green
CVE-ID: CVE-2026-54432
CWE-ID: CWE-79
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Roundcube
Affected software:
Roundcube Webmail
Roundcube Webmail
Detailed vulnerability description
The vulnerability allows a remote user to execute arbitrary script code in a user's browser.
The vulnerability exists due to cross-site scripting in the attachment-validation warning page when rendering an unescaped attachment mime type. A remote user can store a crafted attachment mime type to execute arbitrary script code in a user's browser.
How to mitigate CVE-2026-54432
Install security update from vendor's website.