CVE-2026-85880: Microsoft Windows Heap-Based Buffer Overflow Vulnerability

Q: How do I fix CVE-2026-85880?

windows 10 1607: upgrade to 10.0.14393.9512; windows 10 1809: upgrade to 10.0.17763.9245; windows 10 21h2: upgrade to 10.0.19044.7725. Exact commands for each OS are on this page.

Q: Is CVE-2026-85880 being exploited?

Yes. CVE-2026-85880 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

Q: What does CVE-2026-85880 affect?

CVE-2026-85880 affects windows 10 1607, windows 10 1809, windows 10 21h2. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows ALPC allows an authorized attacker to elevate privileges locally.

Q: How urgent is CVE-2026-85880?

Priority 80/100. High severity; Exploited in the wild (CISA KEV); On your watchlist

Patch now

HIGH 7.8EXPLOITEDWATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-85880 is a high-severity flaw (CVSS 7.8) affecting windows 10 1607, windows 10 1809, windows 10 21h2, reported as exploited in the wild. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Heap-based buffer overflow in Windows ALPC allows an authorized attacker to elevate privileges locally.

Why this priority

High severity
Exploited in the wild (CISA KEV)
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	3.6% (top 11%)
CISA exploited list	Yes, fix due 2026-09-22
Weakness	CWE-122, CWE-908
Published	2026-09-08
Last modified	2026-09-24

Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-09-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-09-08Exploited Added to the CISA Known Exploited Vulnerabilities list
2026-09-08 18:21 UTCPublished CVE record published
2026-09-22Deadline CISA due date for US federal agencies to patch
2026-09-24 23:19 UTCUpdated Record last modified

microsoft windows 10 1607 UPGRADE

Affected: < 10.0.14393.9512

Fixed in: 10.0.14393.9512

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: < 10.0.17763.9245

Fixed in: 10.0.17763.9245

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: < 10.0.19044.7725

Fixed in: 10.0.19044.7725

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: < 10.0.19045.7725

Fixed in: 10.0.19045.7725

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 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: < 10.0.14393.9512

Fixed in: 10.0.14393.9512

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 46 · retext · FIXED · 8.1.0-1.fc46 · FEDORA-2026-0602a84203 · source

sudo dnf upgrade --advisory=FEDORA-2026-0602a84203

Windows 10 Version 1809 for 32-bit Systems · KB5122876 · FIXED · 10.0.17763.9245 · KB5122876 · source

Install KB5122876 via Windows Update, then verify: Get-HotFix -Id KB5122876

Windows 10 Version 1809 for x64-based Systems · KB5122876 · FIXED · 10.0.17763.9245 · KB5122876 · source

Install KB5122876 via Windows Update, then verify: Get-HotFix -Id KB5122876

Windows Server 2019 · KB5122876 · FIXED · 10.0.17763.9245 · KB5122876 · source

Install KB5122876 via Windows Update, then verify: Get-HotFix -Id KB5122876

Windows Server 2019 (Server Core installation) · KB5122876 · FIXED · 10.0.17763.9245 · KB5122876 · source

Install KB5122876 via Windows Update, then verify: Get-HotFix -Id KB5122876

Windows Server 2022 · KB5122882 · FIXED · 10.0.20348.5622 · KB5122882 · source

Install KB5122882 via Windows Update, then verify: Get-HotFix -Id KB5122882

Verify at the official source NVD · CVE Program · CISA KEV catalog · 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-2026-85880?

windows 10 1607: upgrade to 10.0.14393.9512; windows 10 1809: upgrade to 10.0.17763.9245; windows 10 21h2: upgrade to 10.0.19044.7725. Exact commands for each OS are on this page.

Is CVE-2026-85880 being exploited?

Yes. CVE-2026-85880 is on the CISA Known Exploited Vulnerabilities list, so treat it as patch-now.

What does CVE-2026-85880 affect?

CVE-2026-85880 affects windows 10 1607, windows 10 1809, windows 10 21h2. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows ALPC allows an authorized attacker to elevate privileges locally.

How urgent is CVE-2026-85880?

Priority 80/100. High severity; Exploited in the wild (CISA KEV); On your watchlist

Software pages

Windows vulnerabilities · Windows Server vulnerabilities

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References

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