CVE-2020-35730 — Roundcube Webmail Cross-Site Scripting (XSS) Vulnerability

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.

01What is this vulnerability?

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.

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2023-06-22. Ransomware use: Unknown.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Open the Sigma generator with a pre-filled prompt for this CVE to draft a starting detection in your stack of choice:

Open in Sigma generator →

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2020-12-28T19:37:08.000Z
• Last modified: 2025-10-21T23:35:31.104Z
• Added to CISA KEV: 2023-06-22
• BOD 22-01 due: 2023-07-13

09References

• roundcube.net — https://roundcube.net/download/
• github.com — https://github.com/roundcube/roundcubemail/compare/1.4.9...1.4.10
• bugs.debian.org — https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978491
• www.alexbirnberg.com — https://www.alexbirnberg.com/roundcube-xss.html
• github.com — https://github.com/roundcube/roundcubemail/releases/tag/1.4.10
• github.com — https://github.com/roundcube/roundcubemail/releases/tag/1.3.16
• github.com — https://github.com/roundcube/roundcubemail/releases/tag/1.2.13
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…
• lists.fedoraproject.org — https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedorapro…