Microsoft Defender's Unspecified Vulnerability Allows for Denial of Service; CISA's June 3rd KEV Deadline Has Passed

Last refreshed2026-09-27

Status: KEV | Advisory ID: CVE-2026-45498

Key Details

CVE	CVE-2026-45498
Vulnerability Name	Microsoft Defender Denial of Service Vulnerability
Affected products	Microsoft Defender
Exploitation status	Listed in CISA's Known Exploited Vulnerabilities (KEV) catalog, indicating confirmed active exploitation.
KEV listing	Added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2026-05-20.
Exploitation prediction (EPSS)	1.27% probability of exploitation in the next 30 days (69% percentile) -- FIRST.org's EPSS model.
Federal remediation deadline	2026-06-03 (CISA KEV, Binding Operational Directive).

Affected Products, Subsystems & Sectors

Vendor	Product	Affected Versions	Patch Status
Microsoft	Defender

Vendor

Product

Affected Versions

Patch Status

Microsoft

Defender

Subsystems	EWS Engineering Software
Sectors	Multiple

What to Know

Microsoft Defender contains an unspecified vulnerability that allows for denial of service.

What to Do

Monitor Microsoft's web page for any future patch releases.

References

Source	Reference
NVD	https://nvd.nist.gov/vuln/detail/CVE-2026-45498
CVE	https://www.cve.org/CVERecord?id=CVE-2026-45498

Source

Reference

NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-45498

CVE

https://www.cve.org/CVERecord?id=CVE-2026-45498

KEV Required Action

Field	Value
KEV Link	https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Date Added to KEV	2026-05-20
Required Action Due Date	2026-06-03
Required Action	Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Field

Value

KEV Link

https://www.cisa.gov/known-exploited-vulnerabilities-catalog

Date Added to KEV

2026-05-20

Required Action Due Date

2026-06-03

Required Action

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.