Security readout for executives and security teams
Plain-English summary
Roundcube webmail could run attacker-controlled JavaScript when a user views a malicious HTML email containing a crafted SVG. This can expose user data or let an attacker act within that user’s browser session. CISA lists it as known exploited, so affected deployments should be treated as urgent.
Executive priority
Patch affected Roundcube systems promptly, especially public webmail. Although rated medium by CVSS, known exploitation makes delay risky for credential, mailbox, and session exposure.
Technical view
CVE-2023-5631 is stored XSS in Roundcube’s HTML sanitization handling in rcube_washtml.php. A remote unauthenticated attacker can send a crafted HTML email; exploitation requires recipient interaction. Affected versions are before 1.4.15, 1.5.5, and 1.6.4.
Likely exposure
Organizations running self-hosted or provider-managed Roundcube webmail before the fixed releases are exposed. Internet-facing webmail increases risk. The issue is relevant wherever users can receive and view HTML email through Roundcube.
Exploitation context
Active exploitation is supported by CISA KEV listing. Public sources confirm stored XSS, user interaction, and fixed Roundcube releases. The provided evidence does not identify specific campaigns, actor attribution, or exploit volume.
Researcher notes
Focus validation on Roundcube branch and patch level, not generic webmail presence. The root issue is SVG handling during HTML email sanitization. Avoid assuming compromise without log or incident evidence.
Mitigation direction
- Upgrade Roundcube to 1.6.4, 1.5.5, or 1.4.15 based on branch.
- Apply distribution security packages where Roundcube is OS-managed.
- Prioritize internet-facing webmail and high-risk mailboxes.
- Review Roundcube and distribution advisories for branch-specific guidance.
- Monitor webmail activity for suspicious sessions after HTML email viewing.
Validation and detection
- Inventory Roundcube deployments and record exact version numbers.
- Confirm deployed versions are at least 1.4.15, 1.5.5, or 1.6.4.
- Check package manager advisories for applied Debian or Fedora fixes.
- Verify exposed webmail endpoints are behind expected access controls.
- Review logs for unusual webmail activity around suspicious messages.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2023-5631 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.1 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N2.82.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/roundcube/roundcubemail/commit/6ee6e7ae301e165e2b2cb703edf75552e5376613CVE reference
- https://github.com/roundcube/roundcubemail/releases/tag/1.6.4CVE reference
- https://github.com/roundcube/roundcubemail/releases/tag/1.5.5CVE reference
- https://github.com/roundcube/roundcubemail/releases/tag/1.4.15CVE reference
- https://github.com/roundcube/roundcubemail/issues/9168CVE reference
- https://roundcube.net/news/2023/10/16/security-update-1.6.4-releasedCVE reference
- https://github.com/roundcube/roundcubemail/commit/41756cc3331b495cc0b71886984474dc529dd31dCVE reference
- https://roundcube.net/news/2023/10/16/security-updates-1.5.5-and-1.4.15CVE reference
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1054079CVE reference
- https://www.debian.org/security/2023/dsa-5531CVE reference
- https://lists.debian.org/debian-lts-announce/2023/10/msg00035.htmlCVE reference
- https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/LK67Q46OIEGJCRQUBHKLH3IIJTBNGGX4/CVE reference
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-5631CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.