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CVE-2026-78512 Microsoft CVE debrief

CVE-2026-78512 is a numeric truncation error in Microsoft Office Word that allows an unauthorized attacker to execute code over a network. The CVE record was published on 2026-09-08T18:20:46.453Z and has not been modified since then. The NVD entry is currently Analyzed. Defenders should assess exposure and prioritize patching or mitigation in network-connected environments. This vulnerability has significant implications for organizations relying on Microsoft Office Word, particularly those with network-connected installations. A thorough review of the CVE record and NVD detail page is recommended to understand the vulnerability's scope and severity.

Vendor
Microsoft
Product
Microsoft 365 Apps for Enterprise
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-17
Advisory published
2026-09-08
Advisory updated
2026-09-17

Who should care

Defenders responsible for Microsoft Office Word installations, especially in network-connected environments, should assess exposure and prioritize patching or mitigation.

Why it matters

CVE-2026-78512 is a numeric truncation error in Microsoft Office Word that allows an unauthorized attacker to execute code over a network. Defenders should prioritize verifying exposure and applying patches or mitigations.

  • Verify exposure of Microsoft Office Word installations to prevent potential code execution.
  • Apply patches or mitigations to prevent exploitation.
  • Monitor network traffic for suspicious activity related to Microsoft Office Word.

Technical summary

CVE-2026-78512 is a numeric truncation error in Microsoft Office Word that allows an unauthorized attacker to execute code over a network. The vulnerability has a CVSS score of 8.8 and is considered HIGH severity. It affects Microsoft Office Word installations, especially in network-connected environments. Defenders should prioritize verifying exposure and applying patches or mitigations as available from Microsoft. The CVE record and NVD detail page provide information on the vulnerability, but do not specify versions or provide remediation details.

Defensive priority

Defenders should prioritize verifying exposure of Microsoft Office Word installations, especially in network-connected environments, and apply patches or mitigations as available.

Recommended defensive actions

  • Verify exposure of Microsoft Office Word installations, especially in network-connected environments.
  • Apply patches or mitigations as available from Microsoft.
  • Monitor network traffic for suspicious activity related to Microsoft Office Word.

Evidence notes

The CVE record and NVD detail page provide information on the vulnerability, but do not specify versions or provide remediation details. The source reference from Microsoft provides patch information.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-78512 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-78512

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-78512 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-78512

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.