CVE-2026-41108: Windows 10 1607 Privilege Escalation Flaw

CVE-2026-41108 Overview

CVE-2026-41108 is a heap-based buffer overflow vulnerability [CWE-122] in the Microsoft Windows Domain Name System (DNS) component. An authenticated local attacker can exploit the flaw to elevate privileges on the affected host. Microsoft assigned this issue a CVSS 3.1 base score of 7.0, reflecting high impact to confidentiality, integrity, and availability paired with high attack complexity. The vulnerability affects every supported Windows client release from Windows 10 1607 through Windows 11 26H1, plus Windows Server versions 2012 through 2025. Successful exploitation grants the attacker elevated execution context inside the DNS service process, which typically runs with SYSTEM privileges on Windows Server.

Critical Impact

Authenticated local attackers can corrupt heap memory in the Windows DNS component to gain SYSTEM-level privileges across nearly the entire supported Windows fleet.

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

• 2026-06-09 - CVE-2026-41108 published to the National Vulnerability Database
• 2026-06-09 - Microsoft Security Response Center publishes vendor advisory
• 2026-06-11 - NVD record last modified

Technical Details for CVE-2026-41108

Vulnerability Analysis

The vulnerability resides in the Windows DNS component, which handles name resolution and, on server SKUs, authoritative DNS responses. A heap-based buffer overflow occurs when the DNS code writes beyond an allocated heap buffer while processing attacker-influenced data. Because the DNS service runs in a privileged context, corrupting adjacent heap structures lets an attacker hijack control flow or overwrite security-relevant fields. The Common Weakness Enumeration classifies this defect as [CWE-122], heap-based buffer overflow. Microsoft scopes the impact to local privilege escalation, indicating the attacker must already have a low-privileged authenticated session on the target system.

Root Cause

The root cause is missing or insufficient bounds checking on a heap allocation inside the DNS component. When attacker-controlled input exceeds the assumed buffer size, the routine writes past the allocation boundary into adjacent heap metadata or objects. Microsoft has not publicly disclosed the affected function. The EPSS probability is 0.042% at the 13.1 percentile, consistent with a complex local-only attack rather than mass exploitation.

Attack Vector

Exploitation requires local access and low-privileged authenticated execution on the target host. The attacker triggers the vulnerable DNS code path, then shapes heap layout to convert the overflow into arbitrary write or control-flow hijack primitives. High attack complexity reflects timing or memory-layout conditions the attacker must satisfy. No user interaction is required. No public proof-of-concept code or in-the-wild exploitation has been reported, and the issue is not listed in the CISA Known Exploited Vulnerabilities catalog.

No verified exploitation code is publicly available for CVE-2026-41108. Refer to the Microsoft Security Update Guide entry for CVE-2026-41108 for vendor-supplied technical context.

Detection Methods for CVE-2026-41108

Indicators of Compromise

• Unexpected crashes of dns.exe or the DNS Client service with heap corruption exception codes such as 0xC0000374 in the Windows Application event log.
• New processes spawned as SYSTEM from a parent DNS process where DNS would not normally launch child processes.
• Anomalous loaded modules or thread injection into the DNS service process on domain controllers and DNS servers.

Detection Strategies

• Monitor Windows Error Reporting and crash dumps that reference DNS modules for repeated heap corruption faults, which can indicate exploitation attempts that fail before succeeding.
• Correlate authenticated local logons with subsequent privilege changes, token elevation events, or service restarts of the DNS role.
• Apply behavioral endpoint detection rules that flag privilege escalation chains originating from low-integrity processes interacting with the DNS service.

Monitoring Recommendations

• Forward Windows Security, System, and Application event logs to a centralized SIEM and alert on DNS service crashes paired with subsequent SYSTEM process creation.
• Track Sysmon Event ID 1 (process creation) and Event ID 8 (CreateRemoteThread) for activity targeting dns.exe or dnscache.
• Baseline normal DNS server behavior and alert on unusual outbound connections or file writes originating from DNS service processes.

How to Mitigate CVE-2026-41108

Immediate Actions Required

• Apply the Microsoft security update referenced in the MSRC advisory for CVE-2026-41108 to all affected Windows client and server systems.
• Prioritize patching of domain controllers, DNS servers, and any multi-tenant hosts where untrusted users hold local logon rights.
• Audit local accounts and remove unnecessary interactive logon permissions, since exploitation requires an authenticated local session.

Patch Information

Microsoft has released security updates for all listed Windows 10, Windows 11, and Windows Server releases. Administrators should consult the Microsoft Security Update Guide for CVE-2026-41108 to obtain the correct KB article and package for each operating system build. Deploy the updates through Windows Update, Windows Server Update Services (WSUS), Microsoft Intune, or a comparable patch management workflow.

Workarounds

• No vendor-supplied workaround removes the vulnerability without the patch; remediation requires installing the security update.
• Restrict interactive and Remote Desktop logon rights on DNS servers and domain controllers to administrators only, reducing the population of users able to trigger the local attack.
• Enforce least privilege on shared and multi-user systems to limit which accounts can execute code that reaches the vulnerable DNS code path.

# Verify installed updates on a Windows host
wmic qfe list brief /format:table

# Query DNS service status before and after patching
Get-Service -Name DNS | Format-List Name,Status,StartType

# Trigger update scan via Windows Update from an elevated prompt
UsoClient StartScan