High severity · published Aug 17, 2026
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…
7.2
CVSS
0.4%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 38% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
WE
Webmail · Roundcube
1.6.0 before 1.6.18; 1.7.0 before 1.7.3 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-74998
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-74998
Patch
https://github.com/roundcube/roundcubemail/commit/62d33c8a0dc3fd0dd03984220dc9709e8e0de43b
Patch
https://github.com/roundcube/roundcubemail/commit/a2334990c02f7cb77b1a8d6fa97fcd9e1b5cd1fb
Release Notes
https://github.com/roundcube/roundcubemail/releases/tag/1.6.18
Release Notes
https://github.com/roundcube/roundcubemail/releases/tag/1.7.3
Vendor Advisory
https://roundcube.net/news/2026/08/09/security-updates-1.6.18-and-1.7.3
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