CVE Intelligence
CISA KEV Medium Cross-site scripting exploit reference

CVE-2023-5631 — Roundcube Webmail Persistent Cross-Site Scripting (XSS) Vulnerability

Roundcube before 1.4.15, 1.5.x before 1.5.5, and 1.6.x before 1.6.4 allows stored XSS via an HTML e-mail message with a crafted SVG document because of program/lib/Roundcube/rcube_washtml.php behavior. This could allow a remote attacker to load arbitrary JavaScript code.

Published Oct 18, 2023 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, GitHub Security Advisories, CVE Program (cve.org) e CISA ADP · CNA: ESET

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Oct 26, 2023
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • EPSS 75.9% (30-day exploitation probability)+15
  • Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Oct 26, 2023
EPSS FIRST
75.87%
ahead of 100% of scored CVEs · Oct 14, 2026
Affects
Debian
Debian Linux and 3 more
CVSS base
5.4
Medium · 4 source(s)
Prioritization reference: 6.1 provisional

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — bugs.debian.org (NIST National Vulnerability Database)
  • Documented patch — github.com (NIST National Vulnerability Database)
  • Documented patch — github.com (NIST National Vulnerability Database)

CISA required action CISA

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

US federal deadline: Nov 16, 2023 — passed 1064 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Debian Debian Linux, Fedoraproject Fedora, Roundcube Roundcubemail…).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. Apply the fixed version or the patch documented under Remediation.
  4. Exploitation requires user interaction: tighten email/web filtering and warn affected users.
  5. EPSS ahead of 100% of scored CVEs: prioritize it in the patch queue.
  6. Search available logs for exploit probes matching the vulnerability class (cross-site scripting), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Debian Debian Linux version 10.0version 11.0version 12.0 Vulnerable NIST National Vulnerability Database
Fedoraproject Fedora version 39 Vulnerable NIST National Vulnerability Database
Roundcube Roundcubemail ≥ 1.6.0 and < 1.6.3≥ 1.5.0 and < 1.5.4≥ 1.4.0 and < 1.5.14 Vulnerable CVE Program (cve.org) e CISA ADP
Roundcube Webmail < 1.4.15≥ 1.5.0 and < 1.5.5≥ 1.6.0 and < 1.6.4 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
6.1 CVSS 3.1 Medium 2.8 2.7 security@eset.com via NIST National Vulnerability Database
6.1 CVSS 3.1 Medium — — GitHub, Inc. via GitHub Security Advisories
6.1 CVSS 3.1 Medium — — ESET via CVE Program (cve.org) e CISA ADP
5.4 CVSS 3.1 Medium 2.3 2.7 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N (score shown at the top: nvd@nist.gov)
Scoring entities (NIST, CNA, ADP) score independently; each score is shown with its origin. For prioritization we use 6.1 (security@eset.com via NIST National Vulnerability Database) as a conservative provisional reference — not a definitive official score.

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-79 · Cross-site Scripting (XSS)

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Oct 26, 2023
Federal deadline
Nov 16, 2023
passed 1064 day(s) ago
Ransomware use
Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 75.87%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Monitor CSP violation reports and script payloads in reflected parameters.
  • Hunt retroactively in logs from before Oct 26, 2023 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPSapplication logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • Affected products added · roundcube/roundcubemail
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • Affected products added · roundcube/webmail, debian/debian linux, fedoraproject/fedora
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 5.4
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • 2023
  • Added to CISA KEV catalog
    Oct 25, 2023 · CISA
  • CVE published
    Oct 18, 2023 · ESET

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

19 on the record

Elsewhere on this site

Debian
every CVE for this vendor
2023-10
what else CISA listed that month
Cross-site scripting
same class
CWE-79
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-75010 Incorrect Resource Transfer Between Spheres in Roundcube Webmail Aug 17, 2026
  • CVE-2026-75004 Command Injection in Roundcube Webmail Aug 17, 2026
  • CVE-2026-75006 Server-Side Request Forgery (SSRF) in Roundcube Webmail Aug 17, 2026
  • CVE-2026-75007 Command Injection in Roundcube Webmail Aug 17, 2026
  • CVE-2026-75003 Incorrect Resource Transfer Between Spheres in Roundcube Webmail Aug 17, 2026
  • CVE-2026-74997 OS Command Injection in Roundcube Webmail Aug 17, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2023-5631 is "Roundcube Webmail Persistent Cross-Site Scripting (XSS) Vulnerability", rated Medium. It affects Debian Linux (Debian); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 5.4 describes technical severity. EPSS 75.87% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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