CVE-2026-74998

Unvalidated CSS Proxy Response Causing XSS and Information Disclosure in Roundcube Webmail

Published Aug 17, 2026 CVSS 3.1 · 7.2 High EPSS < 1% KEV · Not listed
Description
In Roundcube Webmail before 1.6.18 and 1.7.x before 1.7.3, responses from the CSS (Cascading Style Sheets) proxy were not validated, which may result in information disclosure or XSS (cross-site scripting) via MIME sniffing.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4760-1 roundcube security update
Debian DSA Debian DSA DSA-6479-1 roundcube security update
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title Unvalidated CSS Proxy Response Causing XSS and Information Disclosure in Roundcube Webmail
Type Values Removed Values Added
Description In Roundcube Webmail before 1.6.18 and 1.7.x before 1.7.3, responses from the CSS (Cascading Style Sheets) proxy were not validated, which may result in information disclosure or XSS (cross-site scripting) via MIME sniffing.
First Time appeared Roundcube
Roundcube webmail
Weaknesses CWE-79
CPEs cpe:2.3:a:roundcube:webmail:*:*:*:*:*:*:*:*
Vendors & Products Roundcube
Roundcube webmail
References
Metrics cvssV3_1

{'score': 7.2, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Aug 17, 2026, 4:01 PM
Reserved
Aug 17, 2026, 12:40 PM
Status
Analyzed
Published
Aug 17, 2026, 1:16 PM
Modified
Sep 8, 2026, 7:10 PM