XSS in Roundcube Webmail
CVE-2026-74998
In Roundcube Webmail before 1.6.18 and 1.7.x before 1.7.3, responses from the CSS (Cascading Style Sheets) proxy were not validated, which may result in information disclosure or XSS (cross-site scripting) via MIME sniffing.
Vulnerability class: XSS (Cross-Site Scripting)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N.
EPSS exploit prediction
EPSS: 0.004 (35.8th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 36th percentile — 35.8% 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: +0.002
Affected products
- Roundcube Webmail — versions 1.6.0, 1.7.0
Weakness classification (CWE)
References
- roundcube.net/news/2026/08/09/security-updates-1.6.18-and-1.7.3 (Vendor Advisory)
- github.com/roundcube/roundcubemail/releases/tag/1.6.18 (Release Notes)
- github.com/roundcube/roundcubemail/commit/62d33c8a0dc3fd0dd03984220dc9709e8e0de… (Patch)
- github.com/roundcube/roundcubemail/releases/tag/1.7.3 (Release Notes)
- github.com/roundcube/roundcubemail/commit/a2334990c02f7cb77b1a8d6fa97fcd9e1b5cd… (Patch)
Frequently asked questions
- What is CVE-2026-74998?
- CVE-2026-74998 is a high-severity vulnerability in Roundcube Webmail, classified under Cross-site Scripting. CVSS score: 7.2/10. Published 2026-08-17.
- How severe is CVE-2026-74998?
- High severity. CVSS v3 base score is 7.2 out of 10.