⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 5.5

How to Fix CVE-2026-35419: Out-of-Bounds Read in Windows 11 Version 24H2

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 5.5 - Medium
Actively exploited?Not currently listed in CISA KEV
Affected10.0.26100.0 < 10.0.26100.8457, 10.0.26200.0 < 10.0.26200.8457, 10.0.28000.0 < 10.0.28000.2113, 10.0.26100.0 < 10.0.26100.32860, 10.0.26100.0 < 10.0.26100.32860
Fixed inSee vendor advisory
Type (CWE)CWE-125: Out-of-bounds Read

What is CVE-2026-35419?

CVE-2026-35419 is an out-of-bounds read in Windows 11 Version 24H2. A malformed input causes the product to read memory past the intended buffer boundary, which leaks adjacent process memory and in some cases crashes the service. Vendor description: Out-of-bounds read in Windows DWM Core Library allows an authorized attacker to disclose information locally.

Why this CVE matters

Out-of-bounds read flaws in a network-facing service produce information disclosure today and are routinely the first half of a two-bug chain that ends in code execution.

For deployments of Windows 11 Version 24H2 that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

On Windows, check the product's installed version via Settings - Apps - Installed apps, or run Get-Package from PowerShell to enumerate installed versions.

How to fix CVE-2026-35419

  1. Read the vendor advisory in full: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-35419
  2. Upgrade Windows 11 Version 24H2 to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

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Apply the Microsoft security update for Windows 11 Version 24H2

Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-35419


# Confirm the patch is missing on this host.
Get-Hotfix -ErrorAction SilentlyContinue | Sort-Object InstalledOn -Descending |
  Select-Object -First 10

# Install the latest cumulative + security rollup that ships the fix for Windows 11 Version 24H2.
Install-Module PSWindowsUpdate -Force -SkipPublisherCheck
Import-Module PSWindowsUpdate
Get-WindowsUpdate -AcceptAll -Install -AutoReboot

# After reboot, verify the patched build is in place (10.0.26100.8457).
Get-ComputerInfo -Property WindowsVersion, OsBuildNumber, OsHardwareAbstractionLayer


# Inventory missing patches across many Windows hosts via Ansible (winrm).
ansible windows -m win_updates -a "category_names=SecurityUpdates state=installed"

Verify the fix landed


# Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-35419
# 1. Confirm the running version matches the fixed-in version listed above.

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag this CVE on the patched target.

# 3. Inspect recent service / kernel logs for crash-loops or rollback events.
journalctl -u <service> --since "10 minutes ago"
dmesg --since "10 minutes ago"

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If you cannot patch immediately

Block network reachability to the affected service from untrusted networks. The patched build is the only durable fix; memory-disclosure bugs cannot be fully neutralized at the network layer.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for log entries that do not match your normal request patterns, especially repeated requests to the same uncommon endpoint, and any administrative changes you cannot tie back to a known operator.

Frequently asked questions

Is CVE-2026-35419 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-35419?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for Windows 11 Version 24H2 run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*