Vulnerability Report

CVE-2026-35544

Title: Roundcube Webmail CSS sanitization bypass in HTML e-mail

Other

Proof Of Concept

No public PoC currently indexed for CVE-2026-35544.

CWE Category CWE-669

Published Date Apr 03, 2026

Modified Date Jul 24, 2026

Exploit Status Not Found

Score 5.3 CVSS v3.1

Exploit Probability (EPSS)

0.37%

Vulnerability Summary

CVE-2026-35544: An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. Insufficient Cascading Style Sheets (CSS) sanitization in HTML e-mail messages may lead to a fixed-position mitigation bypass via the use of !important.

Impacted Vendors

cobalt 1

roundcube 1

vdesk 1

Reference Links

https://github.com/roundcube/roundcubemail/commit/099009b9c8e1d3c636fb9a5af72f7c2596018662 https://github.com/roundcube/roundcubemail/commit/226811a1c974271dbedca72672923abaff8191c0 https://github.com/roundcube/roundcubemail/commit/57dec0c127b98e0c8e3b9c26c80049b9c4bcaea7 https://github.com/roundcube/roundcubemail/releases/tag/1.5.14 https://github.com/roundcube/roundcubemail/releases/tag/1.6.14 https://github.com/roundcube/roundcubemail/releases/tag/1.7-rc5 https://roundcube.net/news/2026/03/18/security-updates-1.7-rc5-1.6.14-1.5.14

CVSS v3.1

Source Entity [email protected]

Severity MEDIUM

5.3

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

NONE

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

UNCHANGED

RAW VECTOR CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Associated Attack Patterns (CAPEC)

Total: Patterns