CVE-2026-55001: Improper certificate validation in Windows Active Directory allows an authorized attacker to elevate privilege

Q: How do I fix CVE-2026-55001?

windows 10 1607: upgrade to 10.0.14393.9339; windows 10 1809: upgrade to 10.0.17763.9020; windows server 2016: upgrade to 10.0.14393.9339. Exact commands for each OS are on this page.

Q: Is CVE-2026-55001 being exploited?

CVE-2026-55001 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-55001 affect?

CVE-2026-55001 affects windows 10 1607, windows 10 1809, windows server 2016. Severity is high (CVSS 7.8). Improper certificate validation in Windows Active Directory allows an authorized attacker to elevate privileges locally.

Q: How urgent is CVE-2026-55001?

Priority 38/100. High severity; On your watchlist

Routine

HIGH 7.8WATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-55001 is a high-severity flaw (CVSS 7.8) affecting windows 10 1607, windows 10 1809, windows server 2016. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper certificate validation in Windows Active Directory allows an authorized attacker to elevate privileges locally.

Why this priority

High severity
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-295
Published	2026-07-14
Last modified	2026-07-24

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-07-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-07-14 17:17 UTCPublished CVE record published
2026-07-24 14:18 UTCUpdated Record last modified

microsoft windows 10 1607 UPGRADE

Affected: < 10.0.14393.9339

Fixed in: 10.0.14393.9339

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows 10 1809 UPGRADE

Affected: < 10.0.17763.9020

Fixed in: 10.0.17763.9020

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows server 2016 UPGRADE

Affected: < 10.0.14393.9339

Fixed in: 10.0.14393.9339

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows server 2019 UPGRADE

Affected: < 10.0.17763.9020

Fixed in: 10.0.17763.9020

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows server 2022 UPGRADE

Affected: < 10.0.20348.5386

Fixed in: 10.0.20348.5386

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

microsoft windows server 2025 UPGRADE

Affected: < 10.0.26100.33158

Fixed in: 10.0.26100.33158

Safe to downgrade to: no unaffected older release

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-55001?

windows 10 1607: upgrade to 10.0.14393.9339; windows 10 1809: upgrade to 10.0.17763.9020; windows server 2016: upgrade to 10.0.14393.9339. Exact commands for each OS are on this page.

Is CVE-2026-55001 being exploited?

CVE-2026-55001 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-55001 affect?

CVE-2026-55001 affects windows 10 1607, windows 10 1809, windows server 2016. Severity is high (CVSS 7.8). Improper certificate validation in Windows Active Directory allows an authorized attacker to elevate privileges locally.

How urgent is CVE-2026-55001?

Priority 38/100. High severity; On your watchlist

Software pages

Windows vulnerabilities · Windows Server vulnerabilities · Active Directory vulnerabilities

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References

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