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CVE-2026-55017 Microsoft CVE debrief

CVE-2026-55017 is a high-severity vulnerability in Microsoft Office, allowing unauthorized attackers to execute code locally via a heap-based buffer overflow. The vulnerability has a CVSS score of 7.8 and is classified as HIGH. Microsoft Office 2016, 2019, 2021, and 2024 are affected, with multiple architectures impacted. This vulnerability is based on information from the National Vulnerability Database (NVD) and Microsoft's security advisories. Organizations should prioritize patching to prevent local code execution. The CVE record was published on 2026-07-14T18:18:12.163Z. It is essential to inventory and verify affected Microsoft Office installations and implement compensating controls, such as monitoring for suspicious activity.

Vendor
Microsoft
Product
Microsoft 365 Apps for Enterprise
CVSS
HIGH 7.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-14
Original CVE updated
2026-07-16
Advisory published
2026-07-14
Advisory updated
2026-07-16

Who should care

Organizations using Microsoft Office 2016, 2019, 2021, or 2024 should prioritize patching this vulnerability to prevent local code execution by unauthorized attackers.

Technical summary

The CVE-2026-55017 vulnerability is a heap-based buffer overflow in Microsoft Office. It has been assigned a CVSS score of 7.8 and a severity of HIGH. The vulnerability affects multiple versions of Microsoft Office, including Office 2016, 2019, 2021, and 2024, across various architectures. An unauthorized attacker could exploit this vulnerability to execute code locally.

Defensive priority

High priority should be given to patching CVE-2026-55017 due to its high severity and potential for local code execution.

Recommended defensive actions

  • Apply the official patch from Microsoft
  • Inventory and verify affected Microsoft Office installations
  • Implement compensating controls, such as monitoring for suspicious activity
  • Ensure all users have the latest version of Microsoft Office installed
  • Consider vulnerability scanning and exception tracking

Evidence notes

The CVE-2026-55017 vulnerability is based on information from the National Vulnerability Database (NVD) and Microsoft's security advisories. The vulnerability affects multiple versions of Microsoft Office, and its high severity score indicates a significant risk to organizations using these products.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-55017 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-55017

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

  • CVE-2026-55017 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-55017

    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.