# CVE-2021-1647: Microsoft Defender Remote Code Execution Vulnerability

Source: https://junglewise.ai/threats/cve-2021-1647-microsoft-defender-remote-code-execution-vulnerability  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-11-03. Updated: 2026-05-10  
License: CC BY 4.0 with a link back

CVE-2021-1647 · Severity: critical · CVSS 7.8 · Exploited in the wild · Published 2021-11-03

Microsoft Defender contains a remote code execution vulnerability due to improper handling of files. While classified as RCE, the attack vector is local, requiring an attacker to have basic user privileges to execute the exploit. This vulnerability was confirmed to be exploited in the wild.

Technologies: [Microsoft Defender](https://junglewise.ai/threats/technologies/defender). Vendors: [Microsoft](https://junglewise.ai/threats/vendors/microsoft).

## Quick answers

**Is CVE-2021-1647 exploited in the wild?** Yes. CVE-2021-1647 is known to be exploited in the wild, first recorded on 3 November 2021. Treat it as urgent.

**How severe is CVE-2021-1647?** Critical severity, with a CVSS score of 7.8, published 3 November 2021.

**Which products and versions are affected?** Microsoft Microsoft Defender All versions on supported Windows OS.

**Is there a fix for CVE-2021-1647?** A patch was published on 2021-11-03. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2021-1647 attacked?** It is attacked with local access, in a network appliance.

**Am I affected by CVE-2021-1647?** Check whether you run Microsoft Defender. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Affected products

- Microsoft Microsoft Defender All versions on supported Windows OS

## Timeline

- 2021-11-03: disclosed
- 2021-11-03: kev added: Added to CISA Known Exploited Vulnerabilities Catalog
- 2021-11-03: patched

## Related threats

- [Microsoft Defender null pointer dereference remote code execution](https://junglewise.ai/threats/cve-2026-122194-null-pointer-dereference-in-microsoft-defender-allows-an)
- [Microsoft Defender out-of-bounds read information disclosure](https://junglewise.ai/threats/cve-2026-105726-out-of-bounds-read-in-microsoft-defender-allows-an-authorized)
- [Microsoft Defender Malware Protection Engine elevation of privilege](https://junglewise.ai/threats/cve-2026-69414-microsoft-defender-malware-protection-engine-elevation-of)
- [Microsoft Defender heap buffer overflow](https://junglewise.ai/threats/cve-2026-45584-microsoft-defender-heap-buffer-overflow)
- [Microsoft Defender denial of service](https://junglewise.ai/threats/cve-2026-45498-microsoft-defender-denial-of-service)