CVE-2025-55697: Windows Server 2022 Privilege Escalation

CVE-2025-55697 Overview

CVE-2025-55697 is a heap-based buffer overflow vulnerability in Azure Local, affecting Microsoft Windows Server 2022 23H2 and Windows Server 2025. The flaw allows an authorized local attacker to elevate privileges on the affected host. Microsoft assigned the vulnerability CWE-122 (Heap-based Buffer Overflow) and rated the impact on confidentiality, integrity, and availability as high. Exploitation requires local access and low privileges but no user interaction. Microsoft published the advisory on October 14, 2025, and the entry was last updated in the National Vulnerability Database (NVD) on June 17, 2026.

Critical Impact
A local attacker with low-privileged credentials can corrupt heap memory in Azure Local components to execute code in a higher-privilege context on Windows Server 2022 23H2 and Windows Server 2025.

Affected Products

Microsoft Windows Server 2022 23H2 (Azure Local component)
Microsoft Windows Server 2025 (Azure Local component)
Deployments using Azure Local (formerly Azure Stack HCI)

Discovery Timeline

2025-10-14 - CVE-2025-55697 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-55697

Vulnerability Analysis

CVE-2025-55697 is a heap-based buffer overflow (CWE-122) in Azure Local, Microsoft's hyperconverged infrastructure offering integrated into Windows Server 2022 23H2 and Windows Server 2025. An authenticated local attacker can trigger the overflow by supplying crafted input that exceeds the bounds of a heap-allocated buffer within an Azure Local component. The overflow corrupts adjacent heap metadata or object pointers, giving the attacker control over process execution flow.

Successful exploitation results in privilege escalation on the affected host. Because Azure Local components frequently execute with SYSTEM or high-integrity service accounts, the attacker inherits equivalent privileges. This provides a foothold for lateral movement, persistence, and tampering with the cluster's management plane.

Root Cause

The root cause is improper validation of input length before copying data into a heap buffer allocated by an Azure Local component. Without a bounds check, the memory copy operation writes past the allocation, corrupting neighboring heap chunks. Attackers with predictable heap layouts can shape the overflow to overwrite function pointers, virtual method tables, or synchronization structures used by the higher-privileged service.

Attack Vector

The attack vector is local. The attacker must already hold valid low-privilege credentials on the target host. From that context, the attacker invokes the vulnerable Azure Local interface with a malformed request that carries an oversized payload. No user interaction is required. The vulnerability is not listed on the CISA Known Exploited Vulnerabilities catalog, no public proof-of-concept exists, and no in-the-wild exploitation has been reported. Refer to the Microsoft Security Update CVE-2025-55697 advisory for component-level details.

Detection Methods for CVE-2025-55697

Indicators of Compromise

Unexpected crashes, access violations, or Windows Error Reporting entries associated with Azure Local service processes on Windows Server 2022 23H2 or Windows Server 2025.
New or unexpected child processes spawned by Azure Local service accounts, particularly cmd.exe, powershell.exe, or LOLBins running with elevated tokens.
Local account privilege changes, service creations, or scheduled task additions following anomalous activity by a low-privileged user.

Detection Strategies

Monitor Windows Event Logs for repeated service crashes (Event ID 1000, 1001, 7031, 7034) tied to Azure Local binaries on affected servers.
Baseline expected process lineage for Azure Local service accounts and alert on deviations, especially token elevation or process injection behavior.
Correlate low-privileged interactive logons (Event ID 4624 with logon type 2, 10, or 3) followed by suspicious use of local Azure Local management interfaces.

Monitoring Recommendations

Enable audit policies for process creation with command-line logging (Event ID 4688) across Azure Local cluster nodes.
Ingest endpoint telemetry from cluster nodes into a centralized data lake or SIEM to correlate crash signals with privilege escalation attempts.
Track patch state for the October 2025 and later cumulative updates on all Azure Local hosts and alert on drift.

How to Mitigate CVE-2025-55697

Immediate Actions Required

Apply the Microsoft security update referenced in the MSRC advisory for CVE-2025-55697 to every Azure Local node running Windows Server 2022 23H2 or Windows Server 2025.
Inventory all cluster nodes and confirm patch deployment status; do not rely on partial rollouts across a cluster.
Restrict interactive and remote logon rights on Azure Local hosts to a minimal set of administrators.
Rotate credentials for any low-privileged account that had recent local access to unpatched Azure Local nodes.

Patch Information

Microsoft has published a fix through the standard security update channel. The authoritative reference is the Microsoft Security Update Guide entry for CVE-2025-55697, which lists the applicable KB articles and update packages for Windows Server 2022 23H2 and Windows Server 2025. Deploy updates through Windows Update, Windows Server Update Services (WSUS), or your cluster-aware update tooling.

Workarounds

No official workaround has been published by Microsoft; apply the vendor patch as the primary mitigation.
As an interim compensating control, limit local logon rights on Azure Local nodes to reduce the pool of accounts that can trigger the local attack vector.
Enforce application control (Windows Defender Application Control or AppLocker) on cluster nodes to constrain execution by non-administrative users.

bash

# Example: enumerate installed updates on an Azure Local node to verify patch state
# Replace <KB-ID> with the KB referenced in the MSRC advisory for your build.
Get-HotFix | Where-Object { $_.HotFixID -eq "KB<KB-ID>" }

# Example: restrict interactive logon rights via Group Policy reference
# Computer Configuration > Windows Settings > Security Settings > Local Policies
#   > User Rights Assignment > "Allow log on locally"
# Remove standard user groups; retain only required administrative groups.