What is CVE-2023-43770?

CVE-2023-43770 is a medium-severity vulnerability in Roundcube Webmail, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2023-09-22.

How severe is CVE-2023-43770?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Is CVE-2023-43770 known to be exploited?

Yes. CVE-2023-43770 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-02-12), indicating it is being actively exploited. 8 public proof-of-concept repositories are indexed.

XSS in Roundcube Webmail

CVE-2023-43770

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.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2023-09-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.637 (99.2th percentile), scored 2026-10-18.

High probability of exploitation in the next 30 days — patch promptly. 99th percentile — 99.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.585 · newest: 0.637 · change: +0.052

Affected products

Roundcube Webmail
Debian Linux — versions 10.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

CISA KEV (Known Exploited Vulnerabilities)

This CVE is on the CISA KEV catalog, added on 2024-02-12. CISA KEV inclusion means CISA has confirmed in-the-wild exploitation; US federal agencies are required to remediate within a published due date.

BOD 22-01 due date: 2024-03-04.

Required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Public proof-of-concept exploits

References

github.com/roundcube/roundcubemail/commit/e92ec206a886461245e1672d8530cc93c618a… (Patch)
roundcube.net/news/2023/09/15/security-update-1.6.3-released (Release Notes)
lists.debian.org/debian-lts-announce/2023/09/msg00024.html (mailing-list, Mailing List)
134c704f-9b21-4f2e-91b3-4a467353bcc0 (US Government Resource)

Frequently asked questions

What is CVE-2023-43770?: CVE-2023-43770 is a medium-severity vulnerability in Roundcube Webmail, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2023-09-22.
How severe is CVE-2023-43770?: Medium severity. CVSS v3 base score is 6.1 out of 10.
Is CVE-2023-43770 known to be exploited?: Yes. CVE-2023-43770 is listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-02-12), indicating it is being actively exploited. 8 public proof-of-concept repositories are indexed.