CVE-2026-55012: Microsoft Malware Protection Engine integer overflow code execution

CVE-2026-55012 · Severity: high · CVSS 7.8 · Published 2026-07-14

A security vulnerability exists in Microsoft Defender, the built-in antivirus and security software for Windows. An attacker could exploit this flaw to run unauthorized code on a target system, potentially leading to a full system takeover. While the attack requires a user to perform an action, such as opening a malicious file, it poses a significant risk to data confidentiality and system integrity.

Technologies: Microsoft Malware Protection Engine. Vendors: Microsoft.

Quick answers

Is CVE-2026-55012 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-55012 being exploited in the wild.
How severe is CVE-2026-55012?
High severity, with a CVSS score of 7.8, published 14 July 2026.
Which products and versions are affected?
Microsoft Malware Protection Engine 1.1.0.0 to 1.1.26060.3008.
Is there a fix for CVE-2026-55012?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-55012 attacked?
It is attacked with local access, in an operating system.
Am I affected by CVE-2026-55012?
Check whether you run Microsoft Malware Protection Engine at an affected version. 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.

Technical details

An integer overflow or wraparound vulnerability (CWE-190) exists in the Microsoft Malware Protection Engine, which can lead to a heap-based buffer overflow (CWE-122). The vulnerability is triggered when the engine parses a specially crafted file. An attacker who successfully exploits this could execute arbitrary code in the security context of the LocalSystem account. The attack vector is local, requiring a user to open or interact with a malicious file (User Interaction: Required). The issue affects versions 1.1.0.0 through 1.1.26060.3008 and is addressed in subsequent updates.

Affected products

  • Microsoft Malware Protection Engine 1.1.0.0 to 1.1.26060.3008

Timeline

  • 2026-07-14: advisory: Initial publication by Microsoft and NVD.

References

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