Threats / Roundcube / CVE-2023-5631
CVE-2023-5631
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Roundcube Webmail vulnerability
Roundcube Webmail contains a persistent cross-site scripting vulnerability allowing remote attackers to execute malicious JavaScript code in user browsers.
Verdict
Today item — known-exploited.
A persistent XSS flaw in Roundcube Webmail enables attackers to inject malicious scripts that execute in victim browsers. The vulnerability is actively exploited in the wild with high EPSS score, posing significant risk to webmail users and administrators.
CISA KEV Yes · 2023-10-265EPSS 0.75873 (verify live)6CVSS 6.13CISA SSVC Exploitation: active · Automatable: no · Impact: total4
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
8 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 2023-10-26).
Probability (EPSS)
EPSS 0.75873 — 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 — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-79 Cross-site Scripting (XSS) — weakness family: Web / client.CWE — CNA-assigned (CVE.org); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: totalCISA'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 8 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 a malicious payload and inject it into Roundcube Webmail through user-controllable input that persists in the application.
Business
Webmail users are exposed to arbitrary JavaScript execution within their trusted application context.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I deliver the persistent XSS payload to victims through normal webmail usage, where it executes automatically when they view affected content.
Business
User sessions, credentials, and email data become vulnerable to theft or manipulation without additional user interaction.
3
Lateral reach — past segmentation narrative 3
Attacker
I use the executed JavaScript to steal session tokens, harvest credentials, or redirect users to phishing pages.
Business
Organizational email systems and user accounts face compromise, enabling lateral movement and data exfiltration.
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
Coverage & confidence
— what we know, and what we don’tEstablished (cited)
Coverage gaps — stated, not hidden
Disclosure & credit2
Catalogued by ESETCNA
Credited with finding itMatthieu FaoufinderDenys KlymenkofinderAleksander Machniakremediation developer