CVE-2026-55011 is a CWE-191 integer underflow vulnerability in Microsoft Malware Protection Engine version 1.1.0.0. The flaw involves wrap or wraparound in integer operations, which can be exploited by an unauthorized attacker locally to achieve code execution. The vulnerability has been assigned a CVSS v3.1 base score of 7.8, indicating high severity with high impact on confidentiality, integrity, and availability. Microsoft has released an official patch to remediate this issue, as documented in their security update guide.

Successful exploitation of this integer underflow vulnerability allows an unauthorized local attacker to execute arbitrary code on the affected system. This can lead to full compromise of the system's confidentiality, integrity, and availability.

An official fix is available from Microsoft for Microsoft Malware Protection Engine version 1.1.0.0. Users and administrators should apply the security update provided by Microsoft as detailed in the vendor advisory at https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-55011 to remediate this vulnerability.