What is CVE-2026-35539?

CVE-2026-35539 is a medium-severity vulnerability in Roundcube Webmail, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-03.

How severe is CVE-2026-35539?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Roundcube Webmail

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.

Vulnerability class: XSS (Cross-Site Scripting)

EPSS: 0.003 (16.6th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

Affected products

Roundcube Webmail — versions 0, 1.6.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

cve@mitre.org (Vendor Advisory)
cve@mitre.org (Release Notes)
cve@mitre.org (Patch)
cve@mitre.org (Release Notes)
cve@mitre.org (Patch)
cve@mitre.org (Release Notes)
cve@mitre.org (Patch)

Frequently asked questions

What is CVE-2026-35539?: CVE-2026-35539 is a medium-severity vulnerability in Roundcube Webmail, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2026-04-03.
How severe is CVE-2026-35539?: Medium severity. CVSS v3 base score is 6.1 out of 10.