---
id: "CVE-2017-8540"
kind: "vulnerability"
aliases: ["CVE-2017-8540"]
title: "Microsoft Malware Protection Engine: Microsoft Malware Protection Engine Improper Restriction of Operations Vulnerability"
severity: "critical"
cvss: 9.3
epss: 0.71874
exploited: true
status: "open"
category: "vendor"
products: [{"name": "Microsoft Malware Protection Engine", "fixed": [], "affected": "", "ecosystem": "vendor"}]
ecosystems: ["vendor"]
tags: ["exchange-server", "exploited", "forefront", "microsoft-defender", "vendor", "windows"]
not_affected_if: ["non-windows-hosts"]
published_at: "2017-05-26T20:29:00+00:00"
first_seen_at: "2026-10-23T19:11:52+00:00"
updated_at: "2026-10-23T21:57:35+00:00"
sources: [{"source": "kev", "url": "https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2017-8540", "first_seen_at": "2026-10-23T19:11:52+00:00"}, {"source": "epss", "url": "https://api.first.org/data/v1/epss?cve=CVE-2017-8540", "first_seen_at": "2026-10-23T19:13:44+00:00"}, {"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2017-8540", "first_seen_at": "2026-10-23T21:57:35+00:00"}]
---

# Microsoft Malware Protection Engine: Microsoft Malware Protection Engine Improper Restriction of Operations Vulnerability

The Microsoft Malware Protection Engine, used by Defender and Forefront on Windows and Exchange, mishandles a specially crafted file and causes memory corruption. An attacker who gets such a file scanned can run code remotely, and CISA lists it as actively exploited.

_Summary, check and fix written by a model from the sources; labelled as such._

## Affected

- vendor:Microsoft Malware Protection Engine affected ? fixed ?

## How to check

Check the installed engine version in Microsoft Defender or Windows Security settings and compare it with the fixed engine version in the vendor advisory.

## Fix

Update the Microsoft Malware Protection Engine and Defender platform to the version in Microsoft's advisory, as CISA directs.

## Timeline

- 2026-10-23T19:11:52+00:00 kev https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2017-8540
- 2026-10-23T19:13:44+00:00 epss https://api.first.org/data/v1/epss?cve=CVE-2017-8540
- 2026-10-23T21:57:35+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2017-8540

## From the sources

The Microsoft Malware Protection Engine running on Microsoft Forefront and Microsoft Defender on Microsoft Windows Server 2008 SP2 and R2 SP1, Windows 7 SP1, Windows 8.1, Windows Server 2012 Gold and R2, Windows RT 8.1, Windows 10 Gold, 1511, 1607, and 1703, and Windows Server 2016, Microsoft Exchange Server 2013 and 2016, does not properly scan a specially crafted file leading to memory corruption. aka "Microsoft Malware Protection Engine Remote Code Execution Vulnerability", a different vulnerability than CVE-2017-8538 and CVE-2017-8541.

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_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_