CVE-2026-74998 Cross-site scripting in Webmail
Attackers can exploit unvalidated CSS proxy responses to perform cross-site scripting or disclose information via MIME sniffing in Roundcube Webmail.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74998?
CVE-2026-74998 is a high-severity cross-site scripting vulnerability in Roundcube Webmail, published on 17 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-74998?
It affects 1 product.
Products include Roundcube Webmail.
How do I fix CVE-2026-74998?
Upgrade to a fixed version.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-74998 being exploited?
There is no known exploitation of CVE-2026-74998 in the wild and no public exploit code.
Other vulnerabilities in Roundcube Webmail
Sources
Also known as DEBIAN-CVE-2026-74998, GHSA-6pvc-73xq-46hq, UBUNTU-CVE-2026-74998.