CVE-2026-62799: Heap-based buffer overflow in Windows SMB Client allows an authorized attacker to elevate privileges locally.

Q: How do I fix CVE-2026-62799?

windows 11 26h1: upgrade to 10.0.28000.2704. Exact commands for each OS are on this page.

Q: Is CVE-2026-62799 being exploited?

CVE-2026-62799 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-2026-62799 affect?

CVE-2026-62799 affects windows 11 26h1. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows SMB Client allows an authorized attacker to elevate privileges locally.

Q: How urgent is CVE-2026-62799?

Priority 39/100. High severity; On your watchlist

Routine

HIGH 7.8WATCHLISTUPGRADE

CVE-2026-62799 is a high-severity flaw (CVSS 7.8) affecting windows 11 26h1. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

High severity
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	0.3% (top 75%)
CISA exploited list	No
Weakness	CWE-122
Published	2026-08-11
Last modified	2026-10-23

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

2026-08-11 17:18 UTCPublished CVE record published
2026-10-23 19:10 UTCUpdated Record last modified

microsoft windows 11 26h1 UPGRADE

Affected: < 10.0.28000.2704

Fixed in: 10.0.28000.2704

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 · clementine · FIXED · 1.4.2-1.fc46 · FEDORA-2026-3e748ef4d3 · source

sudo dnf upgrade --advisory=FEDORA-2026-3e748ef4d3

Windows 11 version 26H1 for x64-based Systems · KB5121000 · FIXED · 10.0.28000.2704 · KB5121000 · source

Install KB5121000 via Windows Update, then verify: Get-HotFix -Id KB5121000

Windows 11 Version 26H1 for ARM64-based Systems · KB5121000 · FIXED · 10.0.28000.2704 · KB5121000 · source

Install KB5121000 via Windows Update, then verify: Get-HotFix -Id KB5121000

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-2026-62799?

windows 11 26h1: upgrade to 10.0.28000.2704. Exact commands for each OS are on this page.

Is CVE-2026-62799 being exploited?

CVE-2026-62799 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-2026-62799 affect?

CVE-2026-62799 affects windows 11 26h1. Severity is high (CVSS 7.8). Heap-based buffer overflow in Windows SMB Client allows an authorized attacker to elevate privileges locally.

How urgent is CVE-2026-62799?

Priority 39/100. High severity; On your watchlist

Software pages

Windows vulnerabilities

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References

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