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Vulnerability record · CVE-2017-8538 · published 26 May 2017

CVE-2017-8538: Microsoft Malware Protection Engine memory corruption via crafted file scan

Microsoft · Forefront Security

The Microsoft Malware Protection Engine, used by Forefront, Windows Defender, and Exchange Server, fails to properly scan a specially crafted file, causing memory corruption. Because the engine scans files automatically, a malformed file can trigger the flaw without the user opening it, making it a serious pre-execution risk on affected Windows and Exchange systems.

7.8 CVSS 3.0 High EPSS 50% · top 1.1% CWE-119 · Memory buffer overflow
7.8CVSS 3.0 base score, v2 9.3
50%EPSS exploitation probability, 30 days
NoNot in CISA KEV
3Affected product versions listed by NVD
8References
17 Jun 2026Last modified by NVD

Description

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-2017-8540 and CVE-2017-8541.

CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 20 September 2026. Confidence: high.

high priorityCVSS 7.8 with public exploit code and very high EPSS, but exploitation requires a crafted file to be scanned and no KEV listing or known ransomware use is recorded.

What it is

The Microsoft Malware Protection Engine, used by Forefront, Windows Defender, and Exchange Server, fails to properly scan a specially crafted file, causing memory corruption. Because the engine scans files automatically, a malformed file can trigger the flaw without the user opening it, making it a serious pre-execution risk on affected Windows and Exchange systems.

Impact

An attacker who gets a crafted file scanned by the engine can corrupt memory and potentially execute code in the context of the engine process, which typically runs with high privileges. This can lead to full system compromise on the host.

Attack surface

Reached by delivering a specially crafted file to a system where the Malware Protection Engine scans it, such as via email, web download, or file share. The CVSS vector indicates local access with user interaction required, and no privileges are needed.

Exploitation

Not listed in CISA KEV, but EPSS is 0.5 (98.8th percentile) and a public Exploit-DB entry (42081) exists, indicating exploit code is available and exploitation is plausible.

What to do

  • Apply the Microsoft security update for the Malware Protection Engine immediately; engine updates are typically delivered automatically, so verify the installed engine version is patched.
  • Confirm Exchange Server 2013 and 2016 and all listed Windows versions have the updated engine, since the engine is shared across these products.
  • Restrict untrusted file ingestion paths (email attachments, downloads, shared folders) until patching is confirmed.
  • Monitor Microsoft security advisories for engine version requirements and validate compliance across endpoints and servers.

Detection

  • Track Malware Protection Engine version numbers across endpoints and Exchange servers to identify unpatched instances.
  • Monitor for unexpected crashes or restarts of the engine process (MsMpEng.exe) that could indicate exploitation attempts.
  • Review file scanning logs for repeated failures or anomalies when processing untrusted files.
  • Use endpoint detection to flag suspicious child processes or code execution originating from the engine process.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Affected products

3 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://www.securityfocus.com/bid/98706 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1038571
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8538 Vendor Advisory
https://www.exploit-db.com/exploits/42081/
http://www.securityfocus.com/bid/98706 Third Party AdvisoryVDB Entry
http://www.securitytracker.com/id/1038571
https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8538 Vendor Advisory
https://www.exploit-db.com/exploits/42081/

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

7.8CVE-2026-41091Microsoft Defender link following allows local privilege elevationMicrosoft Defender's malware protection engine resolves links improperly before accessing files, a link-following flaw (CWE-59). A local attacker wit…KEVEPSS 0.44%analysed7.8CVE-2021-1647Microsoft Defender Remote Code Execution VulnerabilityCVE-2021-1647 is a remote code execution flaw in Microsoft Defender, the built-in antivirus and endpoint protection component of Windows, as well as …KEVEPSS 39%analysed7.8CVE-2017-8540Microsoft Malware Protection Engine out-of-bounds write via crafted fileThe Microsoft Malware Protection Engine, used by Windows Defender, Forefront, Security Essentials, System Center Endpoint Protection, Intune Endpoint…KEVEPSS 72%analysed9.3CVE-2013-1346Microsoft malware protection engine memory buffer overflow vulnerabilitympengine.dll in Microsoft Malware Protection Engine before 1.1.9506.0 on x64 platforms allows remote attackers to execute arbitrary code or cause a d…EPSS 12%9.3CVE-2006-5270Microsoft antigen vulnerabilityInteger overflow in the Microsoft Malware Protection Engine (mpengine.dll), as used by Windows Live OneCare, Antigen, Defender, and Forefront Securit…EPSS 30%8.8CVE-2018-0986Microsoft Malware Protection Engine out-of-bounds write enables remote code executionThe Microsoft Malware Protection Engine mishandles a specially crafted file during scanning, causing an out-of-bounds write and memory corruption. Be…EPSS 63%analysed8.1CVE-2026-45584Microsoft malware protection engine heap-based buffer overflow vulnerabilityHeap-based buffer overflow in Microsoft Defender allows an unauthorized attacker to execute code over a network.EPSS 0.71%7.8CVE-2026-69414Microsoft malware protection engine improper access control vulnerabilityMicrosoft is aware of an elevation of privilege in the Microsoft Malware Protection Engine in Microsoft Defender publicly referred to as "Shield…EPSS 0.33%

Source: NIST National Vulnerability Database (record CVE-2017-8538), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.