CVE-2026-55129 Microsoft CVE debrief

Who should care

Users of Microsoft Office, particularly those using 365 Apps, Office 2016, Office 2019, Office 2021, and Office 2024, should be aware of this vulnerability and take steps to mitigate it. The vulnerability has been assigned a CVSS score of 7.8 and a severity of HIGH. Affected operators, platforms, vulnerability-management, and security teams should prioritize patching vulnerable systems.

Technical summary

A heap-based buffer overflow vulnerability exists in Microsoft Office, which could allow an unauthorized attacker to execute code locally. The vulnerability has been assigned a CVSS score of 7.8 and a severity of HIGH. It affects various versions of Microsoft Office, including 365 Apps, Office 2016, Office 2019, Office 2021, and Office 2024. The vulnerability is caused by a heap-based buffer overflow, which can be exploited by an unauthorized attacker to execute code locally.

Defensive priority

High priority should be given to patching vulnerable systems, especially those exposed to untrusted input. Defenders should review compensating controls for exposed systems while remediation is scheduled and verified.

Recommended defensive actions

• Apply patches provided by Microsoft
• Ensure all users have the latest version of Microsoft Office installed
• Restrict access to sensitive areas of the system
• Monitor system logs for suspicious activity
• Implement compensating controls, such as network segmentation

Evidence notes

The CVE record and NVD detail provide information on the vulnerability, its impact, and affected products. Microsoft has provided a patch for the vulnerability. The vulnerability is a heap-based buffer overflow in Microsoft Office, which could allow an unauthorized attacker to execute code locally. The affected products include 365 Apps, Office 2016, Office 2019, Office 2021, and Office 2024. The CVE record was published on 2026-07-14T18:18:19.463Z and has not been modified since then. The NVD entry is currently Analyzed. Defenders should verify the affected scope, severity, and vendor guidance.

Sources and 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.