What is CVE-2026-55011?

CVE-2026-55011 is a high-severity vulnerability in Microsoft Malware Protection Engine, classified under Integer Underflow. CVSS score: 7.8/10. Published 2026-07-14.

How severe is CVE-2026-55011?

High severity. CVSS v3 base score is 7.8 out of 10.

Integer overflow in Microsoft Malware Protection Engine

CVE-2026-55011

Integer underflow (wrap or wraparound) in Microsoft Defender allows an unauthorized attacker to execute code locally.

CVSS v3 metric

CVSS v3 base score 7.8 (High). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H.

Affected products

Microsoft Malware Protection Engine — versions 1.1.0.0

Weakness classification (CWE)

CWE-191 — Integer Underflow

References

secure@microsoft.com (vendor-advisory, patch)

Frequently asked questions

What is CVE-2026-55011?: CVE-2026-55011 is a high-severity vulnerability in Microsoft Malware Protection Engine, classified under Integer Underflow. CVSS score: 7.8/10. Published 2026-07-14.
How severe is CVE-2026-55011?: High severity. CVSS v3 base score is 7.8 out of 10.