*CVE-2026-20862* is a newly disclosed vulnerability in Microsoft Windows Management Services (WMS) affecting various supported Windows versions. It enables local, authorized attackers to access sensitive information they should not typically see. This write-up dives into the technical details, walks through how an exploit would work, and summarizes mitigation steps, keeping language simple and clear for everyone.

What is CVE-2026-20862?

The vulnerability, tracked as CVE-2026-20862, stems from improper access control in the Windows Management Services. An attacker who already has local access but is not highly privileged could abuse misconfigured permissions to access sensitive information (like user credentials, service tokens, or system configuration data) intended only for system admins.

Technical Details

Windows Management Services is responsible for handling system and application management tasks. Due to a logic flaw in the way WMS restricts access to certain log files and configuration dumps, any local user can read potentially sensitive data.

The root problem is found in the access control lists (ACLs) set on temporary files created by WMS — these files may be owned by the SYSTEM but with world-readable permissions.

A typical problematic ACL

Get-Acl C:\Windows\Temp\wms_debug.log

# Output
# FileSystemRights  : FullControl
# AccessControlType : Allow
# IdentityReference : Everyone
# IsInherited       : False

Here, Everyone has read access — this is a misconfiguration.

Let's look at a simple proof-of-concept. Suppose an attacker is logged into a vulnerable system

Step 1: Find interesting files
WMS sometimes writes internal state to %TEMP% or %WINDIR%\Temp with open permissions.

# Find all files created by WMS
Get-ChildItem C:\Windows\Temp\*.log | Select-String "password|token|user"

Step 2: Dump contents

If the attacker sees something like

2026-02-22 07:31:05 - Service startup by SYSTEM
2026-02-22 07:31:05 - Loaded credentials for user: admin
2026-02-22 07:31:05 - Token: eyJeXA...

They have successfully read sensitive log data.

Step 3: Use the data
With privileged tokens or user credentials, the attacker might escalate privileges or pivot to new attacks.

Example to fix permissions

icacls C:\Windows\Temp\wms_debug.log /remove:g Everyone

References

- CVE-2026-20862 on MITRE
- Microsoft Security Advisory - Windows Management Services
- Access Control Lists in Windows

Conclusion

CVE-2026-20862 is not the flashiest bug, but it shows how small configuration mistakes like file permissions can lead to serious leaks. All it takes is a local user to stumble across debug or log files left world-readable, and your system secrets could walk out the door. Lock down permissions, audit sensitive files, and keep your systems patched to stay safe.

If you're a Windows admin, you should check those temp files now!

Timeline

Published on: 01/13/2026 17:56:56 UTC
Last modified on: 01/27/2026 19:14:56 UTC