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MEDIUM · CVSS 6.1 CISA Known Exploited Vulnerability

CVE-2020-35730

Roundcube Webmail Cross-Site Scripting (XSS) Vulnerability

Roundcube Webmail

An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. The attacker can send a plain text e-mail message, with JavaScript in a link reference element that is mishandled by linkref_addindex in rcube_string_replacer.php.

CVSS
6.1
MEDIUM
EPSS
32.9%
30-day exploitation
Ransomware groups
0
recorded exploiting
Published
28 Dec 2020
CWE-79

Exploitation status

CISA Known Exploited Vulnerabilities

Listed by CISA on 22 June 2023. US federal agencies were required to remediate it by 13 July 2023.

EPSS — exploitation probability

FIRST puts the probability of exploitation activity in the next 30 days at 32.9%, which is higher than 98.3% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Frequently asked questions

Is CVE-2020-35730 being exploited by ransomware groups?

No ransomware group in this database is currently recorded as exploiting CVE-2020-35730.

What does CVE-2020-35730 affect?

CVE-2020-35730 affects Roundcube Webmail. An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. The attacker can send a plain text e-mail message, with JavaScript in a link reference element that is mishandled by linkref_addindex in rcube_string_replacer.php.

How severe is CVE-2020-35730?

CVE-2020-35730 is rated MEDIUM with a CVSS base score of 6.1. EPSS puts the probability of exploitation in the next 30 days at 32.9%, higher than 98.3% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 13 July 2023.

How should organisations respond to CVE-2020-35730?

Apply the vendor patch for Roundcube Webmail as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.