CVE-2026-83635: Out-of-bounds read in DNS Server allows an unauthorized attacker to deny service over a network.

Q: How do I fix CVE-2026-83635?

windows server 2012: mitigate or apply the listed mitigation; windows server 2016: upgrade to 10.0.14393.9612; windows server 2019: upgrade to 10.0.17763.9376. Exact commands for each OS are on this page.

Q: Is CVE-2026-83635 being exploited?

CVE-2026-83635 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-2026-83635 affect?

CVE-2026-83635 affects windows server 2012, windows server 2016, windows server 2019. Severity is high (CVSS 7.5). Out-of-bounds read in DNS Server allows an unauthorized attacker to deny service over a network.

Q: How urgent is CVE-2026-83635?

Priority 54/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTMITIGATEUPGRADEUPGRADE

CVE-2026-83635 is a high-severity flaw (CVSS 7.5) 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.

Out-of-bounds read in DNS Server allows an unauthorized attacker to deny service over a network.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.3% (top 29%)
CISA exploited list	No
Weakness	CWE-125
Published	2026-10-13
Last modified	2026-10-16

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-10-13 19:20 UTCPublished CVE record published
2026-10-16 10:45 UTCUpdated 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: < 10.0.14393.9612

Fixed in: 10.0.14393.9612

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: < 10.0.17763.9376

Fixed in: 10.0.17763.9376

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: < 10.0.20348.5761

Fixed in: 10.0.20348.5761

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: < 10.0.26100.33650

Fixed in: 10.0.26100.33650

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.

Exact fixes by distribution

A distro patch exists: prefer upgrading over downgrading.

Fedora ELN · edk2 · FIXED · 20260812-12.eln159 · FEDORA-2026-e316b6370a · source

sudo dnf upgrade --advisory=FEDORA-2026-e316b6370a

Fedora 46 · perl-Mojo-DOM58 · FIXED · 3.003-1.fc46 · FEDORA-2026-d5412af3de · source

sudo dnf upgrade --advisory=FEDORA-2026-d5412af3de

Windows Server 2019 · KB5126651 · FIXED · 10.0.17763.9376 · KB5126651 · source

Install KB5126651 via Windows Update, then verify: Get-HotFix -Id KB5126651

Windows Server 2019 (Server Core installation) · KB5126651 · FIXED · 10.0.17763.9376 · KB5126651 · source

Install KB5126651 via Windows Update, then verify: Get-HotFix -Id KB5126651

Windows Server 2022 · KB5126655 · FIXED · 10.0.20348.5761 · KB5126655 · source

Install KB5126655 via Windows Update, then verify: Get-HotFix -Id KB5126655

Windows Server 2022 (Server Core installation) · KB5126655 · FIXED · 10.0.20348.5761 · KB5126655 · source

Install KB5126655 via Windows Update, then verify: Get-HotFix -Id KB5126655

Windows Server 2025 (Server Core installation) · KB5126646 · FIXED · 10.0.26100.33650 · KB5126646 · source

Install KB5126646 via Windows Update, then verify: Get-HotFix -Id KB5126646

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-2026-83635?

windows server 2012: mitigate or apply the listed mitigation; windows server 2016: upgrade to 10.0.14393.9612; windows server 2019: upgrade to 10.0.17763.9376. Exact commands for each OS are on this page.

Is CVE-2026-83635 being exploited?

CVE-2026-83635 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-2026-83635 affect?

CVE-2026-83635 affects windows server 2012, windows server 2016, windows server 2019. Severity is high (CVSS 7.5). Out-of-bounds read in DNS Server allows an unauthorized attacker to deny service over a network.

How urgent is CVE-2026-83635?

Priority 54/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Windows vulnerabilities · Windows Server vulnerabilities

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References

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