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PatchSiren cyber security CVE debrief

CVE-2026-77504 Microsoft CVE debrief

Microsoft Office Word vulnerability CVE-2026-77504 allows unauthorized attackers to execute code over a network via a double free exploit. The CVE record was published on 2026-09-08T18:20:37.740Z and has not been modified since then. The NVD entry is currently Analyzed. This vulnerability is a high-severity issue that requires immediate attention from defenders, particularly those responsible for Microsoft Office Word installations in networked environments. The vulnerability's CVSS score of 8.8 indicates significant risk, and defenders should assess exposure and apply patches as a high priority.

Vendor
Microsoft
Product
Windows 10 Version 1607
CVSS
HIGH 8.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-09-08
Original CVE updated
2026-09-29
Advisory published
2026-09-08
Advisory updated
2026-09-29

Who should care

Defenders responsible for Microsoft Office Word installations, particularly those in networked environments, should assess exposure and apply patches.

Why it matters

CVE-2026-77504 is a high-severity vulnerability in Microsoft Office Word that requires immediate attention from defenders. The vulnerability allows unauthorized attackers to execute code over a network, posing a significant risk to organizations using affected versions of Microsoft Office Word.

  • Potential code execution over a network
  • High CVSS score indicating significant risk
  • Microsoft Office Word is widely used in many organizations

Technical summary

CVE-2026-77504 is a double free vulnerability in Microsoft Office Word that allows unauthorized attackers to execute code over a network. The vulnerability has a CVSS score of 8.8 and is classified as HIGH severity. This vulnerability affects Microsoft Office Word installations, particularly those in networked environments, and requires immediate attention from defenders. The vulnerability's technical details indicate a high level of risk, and defenders should prioritize assessing exposure and applying patches.

Defensive priority

High priority for defenders to assess exposure and apply patches

Recommended defensive actions

  • Assess exposure of Microsoft Office Word installations to CVE-2026-77504
  • Apply patches provided by Microsoft
  • Verify vulnerability status of affected systems
  • Monitor for potential exploitation attempts

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, including its CVSS score of 8.8 and weaknesses. Microsoft has provided a patch and vendor advisory.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-77504 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-77504

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

  • CVE-2026-77504 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-77504

    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.