CVE‑2026‑45498: Microsoft Defender Denial‑of‑Service Vulnerability
What It Is — Microsoft Defender (the Windows Defender Antivirus engine and related services) contains an unspecified flaw that can be triggered to cause a denial‑of‑service condition. The issue is tracked as CVE‑2026‑45498 and has been added to CISA’s Known Exploited Vulnerabilities (KEV) catalog.
Exploitability — CISA confirms the vulnerability is being actively exploited in the wild. A proof‑of‑concept exists and the CVSS v3.1 base score is 7.5 (High).
Affected Products — Microsoft Defender on supported Windows client and server operating systems (Windows 10, Windows 11, Windows Server 2016‑2022).
Why It Matters for Trust & Control Assurance
- Incident‑response readiness – An exploitable DoS vector tests an organization’s ability to detect, contain, and recover from service‑availability attacks, a core control in most assurance frameworks.
- Patch‑management evidence – Demonstrating timely remediation of a known, actively‑exploited flaw provides defensible audit evidence of due‑diligence.
- Continuous control monitoring – Mapping this vulnerability to the “availability” and “incident response” control objectives enables automated evidence collection for compliance reviews.
Recommended Actions
- Apply Microsoft’s security update for CVE‑2026‑45498 immediately (see Microsoft Security Advisory).
- Verify patch deployment across all endpoints via a centralized configuration‑management tool.
- Update your incident‑response playbook to include detection of abnormal Defender service restarts or resource exhaustion.
- Record remediation steps in your control‑evidence repository to support audit readiness.
Source: CISA KEV – CVE‑2026‑45498