CVE-2026-83935: Heap-based buffer overflow in Microsoft XML allows an unauthorized attacker to execute code over a network.

Q: How do I fix CVE-2026-83935?

windows 10 1607: upgrade to 10.0.14393.9612; windows 10 1809: upgrade to 10.0.17763.9376; windows 10 21h2: upgrade to 10.0.19044.7807. Exact commands for each OS are on this page.

Q: Is CVE-2026-83935 being exploited?

CVE-2026-83935 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-2026-83935 affect?

CVE-2026-83935 affects windows 10 1607, windows 10 1809, windows 10 21h2. Severity is critical (CVSS 9.8). Heap-based buffer overflow in Microsoft XML allows an unauthorized attacker to execute code over a network.

Q: How urgent is CVE-2026-83935?

Priority 62/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

This week

CRITICAL 9.8REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-83935 is a critical-severity flaw (CVSS 9.8) affecting windows 10 1607, windows 10 1809, windows 10 21h2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Heap-based buffer overflow in Microsoft XML allows an unauthorized attacker to execute code over a network.

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-122
Published	2026-10-13
Last modified	2026-10-19

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-19 · 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
2026-10-19 19:20 UTCUpdated Record last modified

microsoft windows 10 1607 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 10 1809 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 10 21h2 UPGRADE

Affected: < 10.0.19044.7807

Fixed in: 10.0.19044.7807

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 22h2 UPGRADE

Affected: < 10.0.19045.7807

Fixed in: 10.0.19045.7807

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 11 23h2 UPGRADE

Affected: < 10.0.22631.7652

Fixed in: 10.0.22631.7652

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 11 24h2 UPGRADE

Affected: < 10.0.26100.9711

Fixed in: 10.0.26100.9711

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

Windows 11 Version 26H2 for ARM64-based Systems · KB5127648 · FIXED · 10.0.26300.9711 · KB5127648 · source

Install KB5127648 via Windows Update, then verify: Get-HotFix -Id KB5127648

Windows 11 Version 26H2 for x64-based Systems · KB5127648 · FIXED · 10.0.26300.9711 · KB5127648 · source

Install KB5127648 via Windows Update, then verify: Get-HotFix -Id KB5127648

Windows 10 Version 1809 for 32-bit Systems · KB5126651 · FIXED · 10.0.17763.9376 · KB5126651 · source

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

Windows 10 Version 1809 for x64-based Systems · KB5126651 · FIXED · 10.0.17763.9376 · KB5126651 · source

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

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

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

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-2026-83935?

windows 10 1607: upgrade to 10.0.14393.9612; windows 10 1809: upgrade to 10.0.17763.9376; windows 10 21h2: upgrade to 10.0.19044.7807. Exact commands for each OS are on this page.

Is CVE-2026-83935 being exploited?

CVE-2026-83935 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-2026-83935 affect?

CVE-2026-83935 affects windows 10 1607, windows 10 1809, windows 10 21h2. Severity is critical (CVSS 9.8). Heap-based buffer overflow in Microsoft XML allows an unauthorized attacker to execute code over a network.

How urgent is CVE-2026-83935?

Priority 62/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action; On your watchlist

Software pages

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References

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