---
id: CVE-2026-55011
title: Microsoft Defender Remote Code Execution Vulnerability
summary: >-
  Integer underflow (wrap or wraparound) in Microsoft Defender allows an
  unauthorized attacker to execute code locally.
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C'
cvssSource: cna
cwe:
  - CWE-191
vendor: Microsoft
product: Microsoft Malware Protection Engine
affected:
  - malware_protection_engine >= 1.1.0.0 < 1.1.26060.3008
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: total
  timestamp: '2026-07-13T00:00:00+00:00'
published: '2026-07-14'
updated: '2026-09-25'
sourceUpdated: '2026-09-25T18:20:21.797Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-55011'
references:
  - url: 'https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55011'
    label: Microsoft Defender Remote Code Execution Vulnerability
tags:
  - cve.org
epss: 0.00466
epssPercentile: 0.3765
ingestedAt: '2026-09-08T17:06:31.929Z'
---

## Overview

Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.

## Affected

- `malware_protection_engine >= 1.1.0.0 < 1.1.26060.3008`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.