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PatchSiren cyber security CVE debrief

CVE-2023-5631 Roundcube CVE debrief

CVE-2023-5631 is a persistent cross-site scripting (XSS) vulnerability in Roundcube Webmail. CISA added it to the Known Exploited Vulnerabilities catalog on 2023-10-26, so defenders should treat it as actively exploited and prioritize remediation before the 2023-11-16 due date. Roundcube’s vendor security-update notices referenced in the source corpus were published on 2023-10-16, and CISA directs organizations to apply vendor mitigations or discontinue use if mitigations are unavailable.

Vendor
Roundcube
Product
Webmail
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2023-10-26
Original CVE updated
2023-10-26
Advisory published
2023-10-26
Advisory updated
2023-10-26

Who should care

Email and webmail administrators, managed service providers, and security teams running Roundcube Webmail—especially where the service is internet-facing or broadly used by end users.

Technical summary

The public record identifies this issue as a persistent XSS flaw in Roundcube Webmail. Persistent XSS can let attacker-controlled content be stored and later rendered to other users, creating risk to webmail sessions and user trust. Because CISA placed the CVE in KEV, the vulnerability should be treated as operationally urgent rather than a routine hardening item.

Defensive priority

High. This is a CISA KEV item with a remediation deadline of 2023-11-16, so affected environments should be patched or mitigated immediately.

Recommended defensive actions

  • Inventory all Roundcube Webmail instances and identify which release branch they are on.
  • Apply the vendor security updates referenced in the official Roundcube notices (including the 1.6.4, 1.5.5, and 1.4.15 update lines, as applicable to your deployment).
  • Follow vendor-provided mitigations as soon as possible; if mitigations are unavailable, discontinue use of the product per CISA guidance.
  • Prioritize internet-facing and externally accessible webmail deployments first.
  • Verify that all servers, containers, and managed-service instances are updated consistently, not just the primary application host.
  • Monitor for unusual webmail behavior or unexpected stored content while remediation is underway.

Evidence notes

This debrief is based only on the supplied CISA KEV record and the official CVE/NVD/CISA links included in the corpus. The corpus identifies CVE-2023-5631 as a persistent XSS issue in Roundcube Webmail, records CISA KEV inclusion on 2023-10-26, and sets a due date of 2023-11-16. The source metadata also points to Roundcube security-update announcements dated 2023-10-16. No full vendor advisory text was provided, so technical detail is intentionally limited to what is explicitly supported by the supplied material.

Official resources

Publicly listed by CISA on 2023-10-26 as a Known Exploited Vulnerability. The supplied corpus references Roundcube security-update announcements dated 2023-10-16, and CISA’s remediation due date is 2023-11-16.