Quantum Secular Labs / Blog / Advisories

CVE-2026-62643: Roundcube Webmail: Server-side request forgery

CVE-2026-62643 is rated critical with a CVSS v3.1 base score of 10.0 and affects Roundcube Webmail. Per its scoring, it can be exploited over the network, without authentication, without any user interaction.

Vulnerability description

In Roundcube Webmail before 1.6.17 and 1.7.x before 1.7.2, 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. NOTE: this issue exists because of insufficient fixes for CVE-2026-35540 and CVE-2026-48843.

Severity breakdown

CVSS v3.1 10.0: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N

  • Attack vector: Network. Exploitable remotely over the network, with no need for local or physical access.
  • Attack complexity: Low. No special conditions; the attack can be repeated reliably.
  • Privileges required: None. No account or prior access is needed.
  • User interaction: None. No action from any user is needed.
  • Scope: Changed. Impact reaches beyond the vulnerable component to other resources.
  • Confidentiality impact: High. Total loss of confidentiality; sensitive data can be fully disclosed.
  • Integrity impact: High. Total loss of integrity; data or system state can be fully modified.
  • Availability impact: None. No effect on availability.

Underlying weakness

CWE-918: Server-Side Request Forgery

The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.

Affected products

  • Roundcube Webmail: from 1.6.0 before 1.6.17; from 1.7.0 before 1.7.2

References