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

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• Yes, if you run Roundcube Webmail. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2024-02-12, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2024-03-04; treat that as the outer limit, not the target.
• EPSS 63.7%, percentile 99: FIRST’s model estimates a 63.7% chance of exploitation activity in the next 30 days, higher than 99% of all scored CVEs (very high). EPSS is a probability, not a verdict.
• Needs a user to click or open something. Phishing makes that realistic, but it is not wormable.

What it is

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/rcubestringreplacer.php behavior.

CISA’s summary

Roundcube Webmail contains a persistent cross-site scripting (XSS) vulnerability that can lead to information disclosure via malicious link references in plain/text messages.

Weakness type: CWE-79.

Product: Roundcube Webmail · Assigned by: mitre · Published: 2023-09-22

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Privileges required: none (no login)
• User interaction: required (a user must click/open something)
• Scope: changed (can affect other components)

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: added 2024-02-12; federal due date 2024-03-04. Known ransomware use: Unknown.
• CISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
• CISA SSVC assessment: exploitation active, automatable no, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 63.66% probability of exploitation activity in the next 30 days; percentile 99.

Timeline

• 2023-09-22 — CVE record published by mitre
• 2024-02-12 — Added to CISA’s Known Exploited Vulnerabilities catalog
• 2024-03-04 — CISA remediation deadline for US federal agencies
• 2025-10-21 — CVE record last updated

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vendor and project advisories, patches

1. Listed in CISA KEV notes (roundcube.net) roundcube.net

Vulnerability records

1. CVE.org record CVE-2023-43770 cve.org
2. NVD entry CVE-2023-43770 nvd.nist.gov

Government

1. CISA Known Exploited Vulnerabilities catalog entry cisa.gov

Other references from the CVE record and advisory

1. github.com github.com
2. [debian-lts-announce] 20230922 [SECURITY] [DLA 3577-1] roundcube security update lists.debian.org

All exploited Roundcube vulnerabilities · Today’s Security Digest