CVE-2026-55012

Think of Microsoft Malware Protection Engine as part of the guardrails that monitor and protect your computer. This bug is like a math mistake in how that component handles certain values—under the right local situation, a bad actor could potentially trick the guardrails into running attacker-controlled code. The result could be complete takeover of the affected computer.

This matters if your business endpoints run Microsoft Malware Protection Engine as part of Microsoft Defender. It’s not something that requires a login to trigger, but the bug does require user interaction and is described as a local attack, so it’s most relevant when an attacker can get someone to open or interact with something on the machine. Because “reachable in default config” is unknown, treat it as a risk when the vulnerable component is reachable and an attacker can induce the required user interaction on the host.

This is a RED issue because it could allow arbitrary code execution on an endpoint, which is the kind of flaw attackers look for to fully compromise a machine. Even though exploitation in the press isn’t clearly documented with dates and there’s no public exploit code on record, the availability of a fixed version means you can reduce exposure immediately. Prioritize patching on all systems that run Microsoft Malware Protection Engine.