CVE-2026-62698: Windows 10 1607 Privilege Escalation Flaw

CVE-2026-62698 Overview

CVE-2026-62698 is a local privilege escalation vulnerability in Microsoft Digest Authentication caused by a numeric truncation error [CWE-197]. An authorized attacker with low privileges can exploit the flaw to elevate privileges on affected Windows and Windows Server systems. The vulnerability affects a broad range of supported operating systems, including Windows 10, Windows 11, and Windows Server editions from 2012 through 2025. Successful exploitation results in high impact to confidentiality, integrity, and availability on the local system.

Critical Impact
Local, low-privileged attackers can escalate to higher privileges on unpatched Windows and Windows Server systems, gaining full control over affected hosts.

Affected Products

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

Discovery Timeline

2026-08-11 - CVE-2026-62698 published to NVD
2026-08-13 - Last updated in NVD database

Technical Details for CVE-2026-62698

Vulnerability Analysis

The vulnerability resides in Microsoft Digest Authentication, a component used to handle HTTP-based digest authentication challenges on Windows systems. A numeric truncation error occurs when a larger integer value is converted or assigned to a smaller integer type, discarding the higher-order bits. The truncated value is then used in subsequent security-relevant operations, producing behavior that differs from the original developer intent. An authorized attacker executing code with low privileges on the local machine can trigger this condition to elevate privileges. Exploitation does not require user interaction and can be performed with low attack complexity.

Root Cause

The underlying weakness is classified under CWE-197: Numeric Truncation Error. Digest Authentication code paths convert or store integer values in a data type too small to hold the full range, resulting in loss of the upper bits. When these truncated values participate in length calculations, buffer indexing, or authorization decisions, they produce incorrect results that an attacker can leverage to corrupt state or bypass intended privilege boundaries.

Attack Vector

The attack vector is local. An attacker must have valid credentials and the ability to execute code on the target system. From that foothold, the attacker interacts with the vulnerable Digest Authentication code path in a way that induces the truncation condition. Because the vulnerable code executes in a higher privilege context, the resulting corruption or logic error grants elevated permissions to the attacker's process. See the Microsoft Security Update Guide for CVE-2026-62698 for authoritative technical detail.

No public proof-of-concept exploit is available for CVE-2026-62698 at the time of publication, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog.

Detection Methods for CVE-2026-62698

Indicators of Compromise

Unexpected creation of processes running under SYSTEM or other elevated tokens that were spawned by low-privileged user sessions.
Anomalous access to Digest Authentication interfaces or wdigest.dll from user-mode processes outside of expected authentication workflows.
Local user accounts suddenly gaining access to resources normally restricted to administrators.

Detection Strategies

Monitor Windows Security event logs for privilege assignment events (Event IDs 4672, 4673, 4674) tied to unexpected parent processes.
Correlate token elevation events with the executing user context to identify low-privileged users obtaining SeDebugPrivilege or SeTcbPrivilege.
Baseline normal use of Digest Authentication in your environment and alert on deviations, particularly from interactive user sessions.

Monitoring Recommendations

Enable command-line and process-creation auditing (Event ID 4688) across all Windows endpoints and servers.
Forward endpoint telemetry to a centralized analytics platform to detect privilege escalation chains that follow initial low-privilege access.
Track patch compliance state for the affected Windows and Windows Server versions to prioritize investigation on unpatched hosts.

How to Mitigate CVE-2026-62698

Immediate Actions Required

Apply the security updates referenced in the Microsoft Security Update Guide for CVE-2026-62698 to all affected Windows and Windows Server systems.
Prioritize patching on multi-user hosts, jump servers, and domain-joined workstations where low-privileged accounts are most likely to obtain a local foothold.
Audit local account membership and remove unnecessary interactive logon rights to reduce the pool of potential attackers.

Patch Information

Microsoft has published fixes through its regular update channels. Consult the Microsoft Security Update Guide for CVE-2026-62698 for the specific KB articles applicable to each Windows 10, Windows 11, and Windows Server build in your environment. Deploy the updates through Windows Update, Windows Server Update Services (WSUS), or your enterprise patch management platform.

Workarounds

No official vendor workaround is documented. Applying the security update is the required remediation.
Restrict local logon rights and enforce the principle of least privilege to reduce exposure until patches are deployed.
Enable attack surface reduction rules and credential protection features such as Credential Guard where supported to limit lateral movement following exploitation.

bash

# Verify patch status for CVE-2026-62698 on Windows hosts
# Replace KBNNNNNNN with the KB identifier listed in the MSRC advisory for your build
Get-HotFix -Id KBNNNNNNN

# Enumerate installed updates and filter by installation date
Get-HotFix | Sort-Object -Property InstalledOn -Descending | Select-Object -First 20