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)
Published · last modified .
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.
EPSS exploit prediction
EPSS: 0.004 (26.7th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 27th percentile — 26.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.003 · newest: 0.004 · change: +0.001
Affected products
- Roundcube Webmail — versions 0, 1.6.0
Weakness classification (CWE)
References
- roundcube.net/news/2026/03/18/security-updates-1.7-rc5-1.6.14-1.5.14 (Vendor Advisory)
- github.com/roundcube/roundcubemail/releases/tag/1.7-rc5 (Release Notes)
- github.com/roundcube/roundcubemail/commit/1b30edf5369668c92fe91dae3d52e477c808a… (Patch)
- github.com/roundcube/roundcubemail/releases/tag/1.6.14 (Release Notes)
- github.com/roundcube/roundcubemail/commit/10a6d1fa8acac85c727b0a6ae4a6642bfa27b… (Patch)
- github.com/roundcube/roundcubemail/releases/tag/1.5.14 (Release Notes)
- github.com/roundcube/roundcubemail/commit/d742954ccbcdee7020f8f2e7c49ce0fca5a0e… (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.