CVE-2023-43770 — Roundcube Webmail Persistent Cross-Site Scripting (XSS) Vulnerability

Roundcube before 1.4.14, 1.5.x before 1.5.4, and 1.6.x before 1.6.3 allows XSS via text/plain e-mail messages with crafted links because of program/lib/Roundcube/rcube_string_replacer.php behavior.

01What is this vulnerability?

Roundcube before 1.4.14, 1.5.x before 1.5.4, and 1.6.x before 1.6.3 allows XSS via text/plain e-mail messages with crafted links because of program/lib/Roundcube/rcube_string_replacer.php behavior.

02Affected products

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

03Active exploitation status

Yes — actively exploited. Added to the CISA KEV catalog on 2024-02-12. 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: 2023-09-22T00:00:00.000Z
• Last modified: 2025-10-21T23:05:36.969Z
• Added to CISA KEV: 2024-02-12
• BOD 22-01 due: 2024-03-04

09References

• github.com — https://github.com/roundcube/roundcubemail/commit/e92ec206a886461245e1672d8530cc…
• roundcube.net — https://roundcube.net/news/2023/09/15/security-update-1.6.3-released
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2023/09/msg00024.html