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PatchSiren cyber security CVE debrief

CVE-2026-21514 Microsoft CVE debrief

CVE-2026-21514 is a Microsoft Office Word issue described as a “Reliance on Untrusted Inputs in a Security Decision” vulnerability. CISA added it to the Known Exploited Vulnerabilities catalog on 2026-02-10 and set a remediation due date of 2026-03-03. Because it is on the KEV list, defenders should treat it as a priority even though the supplied corpus does not include a CVSS score or affected-version details.

Vendor
Microsoft
Product
Office
CVSS
Unknown
CISA KEV
Listed
Original CVE published
2026-02-10
Original CVE updated
2026-02-10
Advisory published
2026-02-10
Advisory updated
2026-02-10

Who should care

Microsoft Office and endpoint administrators, patch-management teams, SOC analysts, and any organization that processes untrusted Word documents or relies on Office hardening controls.

Technical summary

The official vulnerability name indicates a security decision in Word may depend on input that should not be trusted. The supplied corpus does not provide exploit mechanics, affected versions, or a CVSS score. CISA’s KEV listing confirms the issue is considered known to be exploited in the wild and requires timely mitigation per vendor guidance.

Defensive priority

Urgent

Recommended defensive actions

  • Prioritize Microsoft guidance for CVE-2026-21514 and deploy the vendor’s mitigation or update as soon as it is available.
  • Confirm which Office/Word deployments are in scope and verify exposure across managed endpoints and virtual desktops.
  • Track the CISA KEV due date of 2026-03-03 and remediate before that deadline if at all possible.
  • If mitigations are unavailable, follow CISA’s instruction to discontinue use of the product or feature as applicable.
  • Review controls around untrusted Office documents and reinforce safe document-handling practices where feasible.
  • Monitor Microsoft and CISA advisories for any additional mitigation or version-specific guidance.

Evidence notes

This debrief is based only on the supplied CISA KEV record and the official reference links provided in the corpus. The KEV metadata identifies Microsoft as the vendor, Office as the product, the vulnerability name in Word, dateAdded 2026-02-10, dueDate 2026-03-03, and knownRansomwareCampaignUse as Unknown. No CVSS score, affected versions, or exploit details were included in the supplied source set.

Official resources

Publicly disclosed through CISA’s Known Exploited Vulnerabilities catalog on 2026-02-10. The supplied corpus references Microsoft’s update guide and NVD in the KEV entry, but does not include Microsoft patch notes or severity data.