Threats / Roundcube / CVE-2023-43770
CVE-2023-43770
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Roundcube Webmail vulnerability
Roundcube Webmail contains a persistent cross-site scripting vulnerability in plain text message handling that enables information disclosure through malicious link references.
Verdict
Today item — known-exploited.
An attacker can inject malicious scripts into plain text email messages. When a victim views the message, the script executes in their browser session, potentially stealing session tokens, credentials, or sensitive email content. The persistent nature means the payload remains in the system.
CISA KEV Yes · 2024-02-124EPSS 0.58483 (verify live)5Exploit Public PoC6CVSS 6.1 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: partial3
01
Is it exploitable?
— the evidence, ranked above the scoreExploit available
Public proof-of-concept exploit code is cataloged for this vulnerability.We link the existence of the exploit; we do not host or redistribute payloads.
Reported exploitation
10 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2024-02-12).
Probability (EPSS)
EPSS 0.58483 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N) · Affected: Roundcube, Webmail. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 143 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft an email with embedded XSS payload disguised as a link reference in plain text format.
Business
Attacker gains unauthorized access to user email accounts and sensitive communications stored in Roundcube.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I send the malicious email to a target user who opens it in their Roundcube webmail client.
Business
User session is compromised, enabling account takeover and lateral movement within the organization's email infrastructure.
3
Lateral reach — past segmentation narrative 3
Attacker
I exfiltrate authentication tokens or credentials from the victim's active session.
Business
Confidential business communications and personal data are exposed to unauthorized parties.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05