CVE-2026-35540
MEDIUMDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
Exploit Intelligence
Low risk: more likely to be exploited than 23% of all known CVEs.
References
Related Vulnerabilities
Other CWE-669 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2026-31431 | Medium | 5.5 | 100% | KEV | Fix |
| CVE-2002-0055 | Medium | 5.0 | 35% | - | - |
| CVE-2020-1048 | High | 7.8 | 17% | - | - |
| CVE-2021-22900 | High | 7.2 | 14% | KEV | - |
| CVE-2026-25253 | High | 8.8 | 8.0% | - | Fix |
| CVE-2020-6862 | Medium | 5.3 | 6.3% | - | - |
Common questions
How do I fix CVE-2026-35540?
Upgrade roundcube on debian 11 to 1.4.15+dfsg.1-1+deb11u8 or later.
Is CVE-2026-35540 being actively exploited?
Not that we know of. CVE-2026-35540 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.31% is the estimated probability that it will be exploited in the next 30 days. That is higher than 23% of all scored CVEs.
How severe is CVE-2026-35540?
CVE-2026-35540 has a CVSS v3 base score of 5.4, rated medium. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2026-35540 affect?
Published advisories record a fix for roundcube (Debian). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2026-35540
Markdown
[](https://tridentstack.com/cve/CVE-2026-35540)HTML
<a href="https://tridentstack.com/cve/CVE-2026-35540"><img src="https://tridentstack.com/cve/badge/CVE-2026-35540.svg" alt="CVE-2026-35540"></a>Find and fix vulnerabilities across your fleet
TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.
This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-07-24.