Vulnerability in Roundcube Webmail
CVE-2026-35540
An issue was discovered in Roundcube Webmail 1.6.0 before 1.6.14. Insufficient Cascading Style Sheets (CSS) sanitization in HTML e-mail messages may lead to SSRF or Information Disclosure, e.g., if stylesheet links point to local network hosts.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (34.3th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 34th percentile — 34.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: +0.000
Affected products
- Roundcube Webmail — versions 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/579b68eff90650a5c782e153debd66c765648… (Patch)
- github.com/roundcube/roundcubemail/releases/tag/1.6.14 (Release Notes)
- github.com/roundcube/roundcubemail/commit/27ec6cc9cb25e1ef8b4d4ef39ce76d619caa6… (Patch)
Frequently asked questions
- What is CVE-2026-35540?
- CVE-2026-35540 is a medium-severity vulnerability in Roundcube Webmail, classified under Incorrect Resource Transfer Between Spheres. CVSS score: 5.4/10. Published 2026-04-03.
- How severe is CVE-2026-35540?
- Medium severity. CVSS v3 base score is 5.4 out of 10.