CVE-2026-62755: Windows 10 1607 Privilege Escalation Flaw

CVE-2026-62755 Overview

CVE-2026-62755 is a stack-based buffer overflow vulnerability in the Windows Dynamic Host Configuration Protocol (DHCP) Client service. The flaw allows an authorized local attacker to elevate privileges on affected systems. The weakness is tracked under [CWE-121] Stack-based Buffer Overflow and impacts a broad range of Windows client and server releases, including Windows 10, Windows 11, and Windows Server versions from 2012 through 2025.

Microsoft published the advisory on August 11, 2026. Exploitation requires local access and low privileges, but no user interaction. Successful exploitation grants high confidentiality, integrity, and availability impact on the target host.

Critical Impact
Local privilege escalation to SYSTEM through memory corruption in the DHCP Client service across all supported Windows versions.

Affected Products

Microsoft Windows 10 (1607, 1809, 21H2, 22H2) on x86, x64, and ARM64
Microsoft Windows 11 (23H2, 24H2, 25H2, 26H1) on x64 and ARM64
Microsoft Windows Server 2012, 2012 R2, 2016, 2019, 2022, and 2025

Discovery Timeline

2026-08-11 - CVE-2026-62755 published to NVD
2026-08-11 - Microsoft releases security advisory and patch
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-62755

Vulnerability Analysis

The vulnerability resides in the Windows DHCP Client service, a component responsible for obtaining and renewing IP configuration from DHCP servers. A stack-based buffer overflow occurs when the client processes attacker-influenced data using an inadequately bounded stack buffer. Writing past the buffer boundary corrupts adjacent stack memory, including saved return addresses and structured exception handler records.

An authorized local attacker who can trigger the vulnerable code path can overwrite stack control data to hijack execution flow. Because the DHCP Client service runs with elevated privileges, successful exploitation yields SYSTEM-level code execution. The attack is entirely local and does not require user interaction, making it well suited as a post-compromise privilege escalation primitive.

Root Cause

The root cause is improper bounds checking during the parsing or handling of DHCP-related data structures by the client service. The vulnerable function copies variable-length input into a fixed-size stack buffer without validating the length against the destination size. This classic [CWE-121] pattern permits linear stack corruption when crafted input exceeds the expected size.

Attack Vector

Exploitation requires local access and a low-privilege account on the target machine. The attacker interacts with the DHCP Client service, for example by supplying malformed configuration data or triggering the vulnerable parsing path through a controlled network interface or interprocess channel. Once the overflow corrupts stack memory, control transfers to attacker-supplied logic executing in the DHCP Client process context, granting elevation to SYSTEM.

No public proof-of-concept exploit code is available at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. See the Microsoft CVE-2026-62755 Advisory for vendor technical detail.

Detection Methods for CVE-2026-62755

Indicators of Compromise

Unexpected crashes or restarts of the Dhcp (DHCP Client) service recorded in the System event log, particularly Service Control Manager events indicating abnormal termination.
Windows Error Reporting (WER) entries referencing svchost.exe hosting dhcpcore.dll with access violation exception codes such as 0xC0000005.
New or unexpected child processes spawned from svchost.exe instances hosting the DHCP Client service.
Creation of privileged accounts, services, or scheduled tasks shortly after DHCP Client anomalies.

Detection Strategies

Monitor for process lineage anomalies where svchost.exe -k NetworkService spawns interactive shells such as cmd.exe, powershell.exe, or LOLBins.
Correlate DHCP Client service crashes with subsequent privilege escalation indicators on the same host within a short time window.
Deploy behavioral endpoint protection capable of identifying memory corruption exploitation patterns and unexpected token elevation events.
Hunt for anomalous loading of unsigned modules into DHCP Client hosting processes.

Monitoring Recommendations

Enable Windows Event Log forwarding for System, Application, and Security channels to a central SIEM or data lake.
Track patch state for KB updates addressing CVE-2026-62755 across the fleet using vulnerability management tooling.
Alert on repeated Service Control Manager event ID 7031 or 7034 entries for the DHCP Client service.
Baseline expected DHCP Client behavior and flag deviations, including unusual RPC or LPC activity targeting the service.

How to Mitigate CVE-2026-62755

Immediate Actions Required

Apply the Microsoft security update for CVE-2026-62755 to all affected Windows 10, Windows 11, and Windows Server systems as the primary remediation.
Prioritize patching on multi-user systems, jump hosts, and terminal servers where low-privileged users have interactive access.
Audit local account inventories and remove unnecessary standard user accounts on servers and privileged workstations.
Verify that endpoint protection is enabled and up to date to identify exploitation attempts prior to patch deployment.

Patch Information

Microsoft has released security updates for all affected Windows versions. Refer to the Microsoft CVE-2026-62755 Advisory for the specific KB article and download links applicable to each product and architecture. Install the update through Windows Update, WSUS, Microsoft Update Catalog, or your preferred patch management platform, and reboot to complete installation.

Workarounds

No official vendor workaround is published; patching is the required fix.
Where immediate patching is not feasible, restrict interactive and remote local logon rights to trusted administrative accounts only.
Enforce application allowlisting to limit execution of unauthorized binaries by low-privileged users on affected hosts.
Segment and monitor networks so that untrusted DHCP traffic cannot reach sensitive endpoints, reducing the attack surface for related client-side flaws.

bash

# Verify installation of the security update on Windows
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 10

# Check DHCP Client service status
Get-Service -Name Dhcp | Format-List Name, Status, StartType