Vulnerability Report

CVE-2026-35539

Title: XSS in Roundcube Webmail HTML attachment preview

XSS

Proof Of Concept

No public PoC currently indexed for CVE-2026-35539.

CWE Category CWE-79

Published Date Apr 03, 2026

Modified Date Jul 24, 2026

Exploit Status Not Found

Score 6.1 CVSS v3.1

Exploit Probability (EPSS)

0.25%

Vulnerability Summary

CVE-2026-35539: An issue was discovered in Roundcube Webmail before 1.5.14 and 1.6.14. XSS exists because of insufficient HTML attachment sanitization in preview mode. A victim must preview a text/html attachment.

Impacted Vendors

cobalt 1

roundcube 1

vdesk 1

Reference Links

https://github.com/roundcube/roundcubemail/commit/10a6d1fa8acac85c727b0a6ae4a6642bfa27bea1 https://github.com/roundcube/roundcubemail/commit/1b30edf5369668c92fe91dae3d52e477c808aa4f https://github.com/roundcube/roundcubemail/commit/d742954ccbcdee7020f8f2e7c49ce0fca5a0efab 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

6.1

Attack Vector

NETWORK

Complexity

LOW

Privileges

N/A

Interaction

REQUIRED

Confidentiality

N/A

Integrity

N/A

Availability

N/A

Scope

CHANGED

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

Associated Attack Patterns (CAPEC)

Total: Patterns