PatchTheCVECVE-2026-83855: Integer underflow (wrap or wraparound) in Windows WLAN Service allows an unauthorized attacker to deny service
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HIGH 7.5REMOTEWATCHLISTUPGRADEUPGRADEUPGRADE
CVE-2026-83855 is a high-severity flaw (CVSS 7.5) affecting windows 11 23h2, windows 11 24h2, windows 11 25h2. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
Integer underflow (wrap or wraparound) in Windows WLAN Service 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-191 |
| Published | 2026-10-13 |
| Last modified | 2026-10-21 |
Publisher (CNA): Microsoft Corporation · Vendor: microsoft
Last updated 2026-10-21 · 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 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.
microsoft windows 11 25h2 UPGRADE
Affected: < 10.0.26200.9711
Fixed in: 10.0.26200.9711
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.
microsoft windows 11 26h1 UPGRADE
Affected: < 10.0.28000.3231
Fixed in: 10.0.28000.3231
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 26h2 UPGRADE
Affected: < 10.0.26300.9711
Fixed in: 10.0.26300.9711
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.
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
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 2025 (Server Core installation) · KB5126646 · FIXED · 10.0.26100.33650 · KB5126646 · source
Install KB5126646 via Windows Update, then verify:
Get-HotFix -Id KB5126646
Install KB5126646 via Windows Update, then verify:
Get-HotFix -Id KB5126646
Windows 11 Version 25H2 for ARM64-based Systems · KB5127648 · FIXED · 10.0.26200.9711 · KB5127648 · source
Install KB5127648 via Windows Update, then verify:
Get-HotFix -Id KB5127648
Windows 11 Version 25H2 for x64-based Systems · KB5127648 · FIXED · 10.0.26200.9711 · KB5127648 · source
Install KB5127648 via Windows Update, then verify:
Get-HotFix -Id KB5127648
Windows 11 Version 23H2 for ARM64-based Systems · KB5126653 · FIXED · 10.0.22631.7652 · KB5126653 · source
Install KB5126653 via Windows Update, then verify:
Get-HotFix -Id KB5126653
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-2026-83855?
windows 11 23h2: upgrade to 10.0.22631.7652; windows 11 24h2: upgrade to 10.0.26100.9711; windows 11 25h2: upgrade to 10.0.26200.9711. Exact commands for each OS are on this page.
Is CVE-2026-83855 being exploited?
CVE-2026-83855 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-2026-83855 affect?
CVE-2026-83855 affects windows 11 23h2, windows 11 24h2, windows 11 25h2. Severity is high (CVSS 7.5). Integer underflow (wrap or wraparound) in Windows WLAN Service allows an unauthorized attacker to deny service over a network.
How urgent is CVE-2026-83855?
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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