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CVE-2026-69521: Integer overflow or wraparound in Windows iSCSI allows an unauthorized attacker to execute code over a network

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HIGH 8.8WATCHLISTUPGRADEUPGRADEUPGRADE

CVE-2026-69521 is a high-severity flaw (CVSS 8.8) 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.

Integer overflow or wraparound in Windows iSCSI allows an unauthorized attacker to execute code over a network.

Why this priority

  • High severity
  • On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score8.8 (High)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionRequired
EPSS exploit chance0.7% (top 49%)
CISA exploited listNo
WeaknessCWE-190
Published2026-10-13
Last modified2026-10-23
Publisher (CNA): Microsoft Corporation · Vendor: microsoft

Last updated 2026-10-23 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

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

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 · 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-2026-69521?

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-2026-69521 being exploited?

CVE-2026-69521 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-2026-69521 affect?

CVE-2026-69521 affects windows 10 1607, windows 10 1809, windows 10 21h2. Severity is high (CVSS 8.8). Integer overflow or wraparound in Windows iSCSI allows an unauthorized attacker to execute code over a network.

How urgent is CVE-2026-69521?

Priority 48/100. High severity; On your watchlist

Software pages

Windows vulnerabilities

Related CVEs

References

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