Medium 4.0Known exploited (CISA KEV)Published May 20, 2026

CVE-2026-45498Microsoft Defender Denial of Service Vulnerability

Updated under an hour ago (2026-10-19 04:50 UTC)

Does this affect you?

It affects Microsoft Defender Antimalware Platform. Add what you run to find out whether that includes you.

CISA lists it as known exploited since May 20, 2026; federal agencies had to remediate by Jun 3, 2026. Treat that date as your deadline.

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Exploited in the last 30 days

Microsoft Defender Denial of Service Vulnerability

CVSS: 4.0 MEDIUM (v3.1, CNA)CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L/E:U/RL:O/RC:C
Weakness (CWE): CWE-400
Known exploited: Added to CISA KEV May 20, 2026; federal remediation due Jun 3, 2026Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
EPSS (exploitation in the next 30 days): 1.27% (percentile 69)
Assigned by: microsoft
NVD analysis: Analyzed
Record last updated: Aug 10, 2026
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Microsoft Microsoft Defender Antimalware Platform microsoft:defender_antimalware_platform (from the name)	from 4.0.0.0 before 4.18.26040.7	CNA record
microsoft defender_antimalware_platform microsoft:defender_antimalware_platform	before 4.18.26040.7	NVD

References

https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-45498vendor-advisory, patch
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-45498third-party-advisory, us-government-resource

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.