Threat Intelligence / CVE / CVE-2023-43770

CVE-2023-43770 — Roundcube Webmail

CISA KEV
CVSS v3.1 6.1 (MEDIUM) · EPSS 80.3% (higher than 99.1% of all scored CVEs) · Priority 9/10 · Published 2023-09-22

As of 2025-10-31, CVE-2023-43770 is a MEDIUM-severity vulnerability in Roundcube Webmail, CVSS v3.1 6.1, EPSS 80.3% (99.1th percentile). It is listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-02-12), with a US federal remediation deadline of 2024-03-04. Threadlinqs Intelligence links 1 tracked threat campaign to CVE-2023-43770, most recently “APT28/UAC-0001 Sustained Cyber Espionage Against Ukraine & EU (2024-2026 New TTPs)”.

Last updated: 2025-10-31

What is 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.

The record classifies CVE-2023-43770 under weakness class CWE-79. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs a user to take an action first. 2 affected-product entries are recorded, across 2 vendors, listed below. The identifier was first published 1087 days ago.

Severity and exploitation probability

CVSS v3.1 base score
6.1 — MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
EPSS (FIRST)
80.3% probability of exploitation in the next 30 days, higher than 99.1% of all scored CVEs
CISA KEV
Listed since 2024-02-12, federal remediation deadline 2024-03-04
Threadlinqs priority
9/10 — CISA KEV-listed, which Threadlinqs floors at 9
Published
2023-09-22, last modified 2025-10-31

Is CVE-2023-43770 being exploited?

CISA added CVE-2023-43770 to the Known Exploited Vulnerabilities catalog on 2024-02-12, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2024-03-04 under BOD 22-01. It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.

Affected products and versions

How to fix CVE-2023-43770

The record marks a vendor fix as available for CVE-2023-43770. Patch reference: https://github.com/roundcube/roundcubemail/releases/tag/1.6.3. Vendor advisory: https://github.com/roundcube/roundcubemail/commit/e92ec206a886461245e1672d8530cc93c618a49b. Because CVE-2023-43770 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2024-03-04. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.

Threat activity tracking CVE-2023-43770

1 tracked threat in the Threadlinqs corpus references CVE-2023-43770, either in the campaign’s CVE list or as an indicator on the campaign record.

Sources

Seeded from kev and not yet processed by the Threadlinqs enrichment pipeline, so blank CVSS, EPSS or KEV fields above mean NOT MEASURED rather than measured-absent.

Full detection coverage & IOCs for threats exploiting CVE-2023-43770 are available via the Threadlinqs MCP server (Purple tier). View plans →

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