CVE-2026-62893: Windows Deployment Services UAF Vulnerability

CVE-2026-62893 Overview

CVE-2026-62893 is a use-after-free vulnerability in Windows Deployment Services (WDS) that allows an unauthorized attacker to execute code over a network. The flaw is tracked under CWE-416 and carries a CVSS 3.1 score of 9.8. Exploitation requires no authentication, no user interaction, and can be triggered remotely across the network. Successful exploitation compromises confidentiality, integrity, and availability of the affected host. Because WDS runs on servers that provision operating systems to network clients, a compromised deployment server can be used to pivot deeper into an enterprise environment.

Critical Impact
Unauthenticated remote code execution against Windows Deployment Services with no user interaction required.

Affected Products

Windows Deployment Services (WDS) role on Windows Server
Refer to the Microsoft Security Update Guide CVE-2026-62893 for the full list of affected builds
Any Windows Server acting as a PXE/WDS provisioning host

Discovery Timeline

2026-08-11 - CVE-2026-62893 published to NVD
2026-08-12 - Last updated in NVD database

Technical Details for CVE-2026-62893

Vulnerability Analysis

CVE-2026-62893 is classified as a use-after-free (CWE-416) condition in Windows Deployment Services. Use-after-free vulnerabilities occur when a program continues to reference memory after that memory has been released. An attacker who can influence the freed object's contents can cause the process to execute attacker-controlled data as code or pointers.

WDS listens for PXE and TFTP requests from network clients during operating system provisioning. Because the service handles unauthenticated network input as part of its core function, an attacker on the same network segment can reach the vulnerable code path without credentials. The service typically runs with elevated privileges on a Windows Server, which extends the impact of successful exploitation.

The EPSS score for CVE-2026-62893 sits at roughly 1.85% with a 77th percentile ranking, indicating higher-than-average predicted exploitation activity compared to the broader CVE population.

Root Cause

The root cause is improper memory lifecycle management inside a Windows Deployment Services component. A code path releases an object while another reference to the same object remains reachable. Subsequent operations against the stale reference read or write to reclaimed memory, enabling control-flow hijacking when the freed region is reallocated with attacker-influenced data.

Attack Vector

The attack vector is network-based with low complexity and no privileges required. An attacker sends crafted requests to a WDS server exposed on the network. No user on the target machine needs to interact with the payload. Environments that expose WDS to broad network segments, guest VLANs, or non-hardened provisioning subnets face the highest exposure.

Microsoft has not publicly released technical exploitation details. See the Microsoft Security Update Guide CVE-2026-62893 advisory for build-specific technical guidance.

Detection Methods for CVE-2026-62893

Indicators of Compromise

Unexpected crashes, restarts, or access violations in the WDSServer service or wdsserver.exe process.
Anomalous PXE, TFTP (UDP/69), or WDS multicast traffic originating from hosts that are not provisioning candidates.
New or unexpected child processes spawned by the WDS service account on deployment servers.
Outbound connections initiated by a WDS server to untrusted external hosts following inbound PXE/TFTP traffic.

Detection Strategies

Monitor Windows Event Logs on WDS servers for service faults, WER crash reports, and unexpected restarts of WDS-related services.
Correlate network telemetry for PXE and TFTP traffic against a known allowlist of client subnets and MAC address ranges.
Alert on process creation events where wdsserver.exe or the WDS host process spawns shells, scripting engines, or LOLBins.
Baseline normal WDS request volumes and flag deviations that suggest scanning or brute exploitation attempts.

Monitoring Recommendations

Forward WDS server telemetry, including process, network, and Windows Event data, to a centralized analytics platform for correlation.
Enable EDR behavioral policies on all Windows Server hosts running the WDS role to catch post-exploitation activity.
Track service account authentication activity from WDS servers to detect lateral movement following a compromise.
Review firewall and network segmentation logs for PXE/TFTP traffic crossing security boundaries.

How to Mitigate CVE-2026-62893

Immediate Actions Required

Apply the security update referenced in the Microsoft Security Update Guide CVE-2026-62893 to all Windows Servers running the WDS role.
Inventory every host with the Windows Deployment Services role installed, including test and lab environments.
Restrict network reachability to WDS servers so that only authorized provisioning subnets can send PXE and TFTP traffic.
If a WDS server is no longer in active use, remove the role rather than leaving it installed and exposed.

Patch Information

Microsoft has published guidance and security updates for CVE-2026-62893 in the Microsoft Security Update Guide. Administrators should identify affected Windows Server builds through the advisory and deploy the corresponding cumulative update. Verify patch installation via Get-HotFix or Windows Update history after deployment.

Workarounds

Disable or uninstall the Windows Deployment Services role on servers where it is not required.
Block inbound UDP/67, UDP/69, and UDP/4011 at network boundaries that do not need to serve PXE clients.
Isolate WDS servers on a dedicated, tightly controlled provisioning VLAN.
Enforce strict host-based firewall rules to limit which clients can initiate PXE and TFTP sessions to the WDS host.

bash

# Verify whether the WDS role is installed and disable it if not needed
Get-WindowsFeature -Name WDS
Uninstall-WindowsFeature -Name WDS -Remove

# Confirm the security update is present (replace KB number with the one from the advisory)
Get-HotFix | Where-Object { $_.HotFixID -eq 'KBXXXXXXX' }