In July 2023, Microsoft patched a critical vulnerability identified as CVE-2023-36876, which affected the Reliability Analysis Metrics Calculation (RacTask) component in Windows. This vulnerability was classified as an Elevation of Privilege (EoP) issue, meaning it potentially allowed local attackers to gain higher privileges on the system, such as SYSTEM-level access. Let's break down what went wrong, how attackers could exploit this, and how you can protect your systems.

What is RacTask?

RacTask is a scheduled task in Windows associated with RacAgent and the Reliability Analysis Component. It generally runs under the SYSTEM account and is responsible for collecting reliability and performance data for the Windows Reliability Monitor. Because it runs with high privileges, any bug in handling permissions or execution context could allow a less-privileged user to escalate rights.

The Issue

The vulnerability centers around improper checking of permissions when invoking or interacting with the RacTask scheduled task. A user with limited privileges could trigger the task or manipulate files or commands it handles, leading it to execute code of their choosing as SYSTEM.

Microsoft describes it as:  
> “An attacker who successfully exploited this vulnerability could gain SYSTEM privileges.”

Who is Affected?

- Operating Systems: Primarily Windows 10 and Windows Server versions still under support as of July 2023.

How Attackers Exploit CVE-2023-36876

Attackers look for ways to use scheduled tasks like RacTask to execute their code with SYSTEM privileges. If the task references resources like scripts or files located in directories writable by non-privileged users, or if the task's permissions can be abused, an attacker can replace, modify, or trigger execution in an unsafe way.

Let's walk through a simplified exploit scenario—for educational purposes only.

You can list scheduled tasks using

Get-ScheduledTask | Where-Object {$_.TaskName -like "*Rac*"}

You’ll usually see \Microsoft\Windows\RAC\RacTask.

Some versions of Windows may have misconfigured ACLs for this task. To check

Get-ScheduledTask -TaskName "RacTask" | Get-ScheduledTaskInfo
(Get-Acl "C:\Windows\System32\Tasks\Microsoft\Windows\RAC\RacTask").Access

If a local user has write or modify rights, this is a potential attack vector.

Suppose the task launches a script or binary that the user can replace

# Hypothetical vulnerable command launched by RacTask
Start-Process "C:\ProgramData\RacAgent\collectdata.ps1"

# If 'collectdata.ps1' is user-writable:
echo 'Start-Process cmd.exe -ArgumentList "/c net localgroup administrators hacker /add"' > "C:\ProgramData\RacAgent\collectdata.ps1"

User triggers the task

schtasks /Run /TN "\Microsoft\Windows\RAC\RacTask"

Now, the code runs as SYSTEM, adding "hacker" to the Administrators group.

Real-World Exploit Example

Security researcher Orca Security published a detailed analysis exploiting a similar vulnerability. The concept revolves around a *user-writable resource or misconfigured task trigger*. You can find more technical details and exploits at:

- Microsoft Advisory
- Orca Security Analysis
- SecureAuth Labs (*sandbox escape variant*)

How to Protect Your Systems

1. Apply Patch: Microsoft fixed this in July 2023 Patch Tuesday. Get updates here.

Audit ACLs: Regularly check scheduled task permissions with PowerShell or GUI tools.

3. Monitor for Suspicious Task Activity: Use logs and EDR tools to detect abnormal scheduled task behavior.
4. Limit User Write Access: Avoid configurations where standard users can write to folders/scripts executed by SYSTEM tasks.

Conclusion

CVE-2023-36876 is an important reminder that even “quiet” Windows components like RacTask can be a springboard for privilege escalation if not secured properly. Untrusted users and SYSTEM tasks do not mix! With scheduled tasks being everywhere in Windows, keep an eye on what they run—and who can edit their resources.

Stay patched, stay safe.

References  
- Microsoft: CVE-2023-36876  
- Orca Security: Analysis Article  
- SecureAuth Labs: CVE-2023-36876 Writeup  

Author: [YourName]  
Date: June 2024

Timeline

Published on: 08/08/2023 18:15:00 UTC
Last modified on: 08/11/2023 13:02:00 UTC