Windows Hyper-V Denial of Service Vulnerability

published 2021-07-14 5 y ago modified 2026-08-10 2 mo ago also EUVD-2021-20432

cvss: 8.6; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 3.1%; EPSS 3.1% chance of exploitation in 30 days, percentile 87%
public exploits: 0; none known

Patch / fix

fixed in 8 links 2

Microsoft Windows 10 Version 1809 10.0.17763.2061
Microsoft Windows 10 Version 1909 10.0.18363.1679
Microsoft Windows 10 Version 2004 10.0.19041.1110
Microsoft Windows 10 Version 21H1 10.0.19043.1110
Microsoft Windows Server 2019 10.0.17763.2061
Microsoft Windows Server 2019 (Server Core installation) 10.0.17763.2061
Microsoft Windows Server version 2004 10.0.19041.1110
Microsoft Windows Server version 20H2 10.0.19042.1110

Exploit prediction

3.14% chance of exploitation in the next 30 days, higher than 87% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
CNA	3.1	6.3	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H/E:U/RL:O/RC:C
CNA	3.1	6.3	CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H
CNA	3.1	8.6	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
NVD	2.0	5.0	AV:N/AC:L/Au:N/C:N/I:N/A:P

Affected products

Microsoft Windows 10 Version 1809
Microsoft Windows 10 Version 1909
Microsoft Windows 10 Version 2004
Microsoft Windows 10 Version 21H1
Microsoft Windows Server 2019
Microsoft Windows Server 2019 (Server Core installation)
Microsoft Windows Server version 2004
Microsoft Windows Server version 20H2

References

msrc.microsoft.com /update-guide/vulnerability/CVE-2021-33755
vendor-advisory, patch
portal.msrc.microsoft.com /en-US/security-guidance/advisory/CVE-2021-33755
patch, vendor-advisory

Sources

CVE List CVE-2021-33755
NVD CVE-2021-33755

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary