What is CVE-2026-45498?
Microsoft Defender Denial of Service Vulnerability
The record classifies CVE-2026-45498 under weakness class CWE-400. Its CVSS v3 base vector states that the flaw requires local access to the host, needs no prior authentication, needs no user interaction. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 161 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 4 — MEDIUM
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 - EPSS (FIRST)
- 1.2% probability of exploitation in the next 30 days, higher than 68.9% of all scored CVEs
- CISA KEV
- Listed since 2026-05-20, federal remediation deadline 2026-06-03 — used in known ransomware campaigns
- Threadlinqs priority
- 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- Published
- 2026-05-20, last modified 2026-08-10
Is CVE-2026-45498 being exploited?
CISA added CVE-2026-45498 to the Known Exploited Vulnerabilities catalog on 2026-05-20, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2026-06-03 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2026-45498 is publicly available. 1 public proof-of-concept repository is tracked for this identifier. It currently carries a trending score of 40 in the Threadlinqs vulnerability feed.
Affected products and versions
- Microsoft: Defender Antimalware Platform
How to fix CVE-2026-45498
Because CVE-2026-45498 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2026-06-03. No vendor patch reference has been recorded for CVE-2026-45498 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.
Threat activity tracking CVE-2026-45498
2 tracked threats in the Threadlinqs corpus reference CVE-2026-45498, either in the campaign’s CVE list or as an indicator on the campaign record.
- NightmareEclipse Coordinated Disclosure Breach Campaign: 9+ Windows Zero-Days (CVE-2026-33825, CVE-2026-41091, CVE-2026-45498, CVE-2026-45585, CVE-2026-45586) Dumped Outside Responsible Disclosure and Weaponized in Real-World Intrusions — CRITICAL · 2026-08-04
- CISA KEV Catalog Adds Seven Vulnerabilities (May 20, 2026) — Microsoft Defender CVE-2026-41091 (EoP) and CVE-2026-45498 (DoS) Headline Active Exploitation Batch — HIGH · 2026-05-21
Sources
Enriched from CVE.org, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories. Last verified by Threadlinqs on .