CVE-2026-55129: Microsoft Office Remote Code Execution Vulnerability

highCVSS 7.8CVE-2026-55129

Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.

CSIRTS triage

vendor: Microsoft product: Office Remote code execution

What: Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code locally.
Who is affected: Users of Microsoft Office are affected.
Urgency: Remediation is high urgency due to the potential for remote code execution, although no exploitation is reported yet.
Action: Update to the latest version of Microsoft Office.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: high — CVSS 7.8
Published: 2026-07-14
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55129

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-551290.34% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 27% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-55129	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

unknownexploitedNCSC-2026-0237 [1.02] [H/H] Vulnerabilities Fixed in Microsoft Officencsc-nl
unknownexploitedNCSC-2026-0237 [1.01] [H/H] Vulnerabilities fixed in Microsoft Officencsc-nl
unknownexploitedNCSC-2026-0237 [1.00] [M/H] Vulnerabilities fixed in Microsoft Officencsc-nl
highCVE-2026-55129: Heap-based buffer overflow in Microsoft Office allows an unauthorized attacker to execute code…nvd

Recent advisories for Microsoft Office Remote

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-55022: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-07-14
highCVE-2026-55056: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-07-14
highCVE-2026-47290: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-07-14
highCVE-2026-55017: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-07-14
highCVE-2026-50301: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-07-14
highCVE-2026-50467: Microsoft Office Remote Code Execution Vulnerabilitymsrc · 2026-07-14