PatchTheCVECVE-2026-35420: Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.
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Routine
HIGH 7.8WATCHLISTMITIGATEUPGRADEUPGRADE
CVE-2026-35420 is a high-severity flaw (CVSS 7.8) affecting windows server 2012, windows server 2016, windows server 2019. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Heap-based buffer overflow in Windows Kernel 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 75%) |
| CISA exploited list | No |
| Weakness | CWE-122 |
| Published | 2026-05-12 |
| Last modified | 2026-10-26 |
Publisher (CNA): Microsoft Corporation · Vendor: microsoft
Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
microsoft windows server 2012 MITIGATE
Affected: all versions · r2
Fixed in: no fixed release known
Safe to downgrade to: a release before r2
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: < 10.0.14393.9140
Fixed in: 10.0.14393.9140
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: < 10.0.17763.8755
Fixed in: 10.0.17763.8755
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: < 10.0.20348.5074
Fixed in: 10.0.20348.5074
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 23h2 UPGRADE
Affected: < 10.0.25398.2330
Fixed in: 10.0.25398.2330
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: < 10.0.26100.32772
Fixed in: 10.0.26100.32772
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.
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-2026-35420?
windows server 2012: mitigate or apply the listed mitigation; windows server 2016: upgrade to 10.0.14393.9140; windows server 2019: upgrade to 10.0.17763.8755. Exact commands for each OS are on this page.
Is CVE-2026-35420 being exploited?
CVE-2026-35420 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-2026-35420 affect?
CVE-2026-35420 affects windows server 2012, windows server 2016, windows server 2019. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows Kernel allows an authorized attacker to elevate privileges locally.
How urgent is CVE-2026-35420?
Priority 38/100. High severity; On your watchlist
Software pages
Windows vulnerabilities · Windows Server vulnerabilities
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