Windows CMSTP UAC Bypass Attempt via Autoelevate COM Object DllHost Execution

ATT&CK techniques

Priv Esc → Defense Evasion

Recon
Resource Dev
Initial Access
Execution
Persistence
Priv Esc
- T1548.002Bypass User Account Control
Defense Evasion
- T1218.003CMSTP
- T1548.002Bypass User Account Control
Cred Access
Discovery
Lateral Movement
Collection
C2
Exfiltration
Impact

What it detects

This rule flags process creation events where the parent process is DllHost.exe with command lines that include specific COM Processid values tied to CMSTP-enabled autoelevate COM objects. UAC bypass techniques matter because they aim to obtain elevated execution without prompting the user. The detection relies on process creation telemetry, focusing on the parent image and parent command-line content plus high/system integrity levels.

Reporting behind it

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Windows CMSTP UAC Bypass Attempt via Autoelevate COM Object DllHost Execution

Pivot detection · T1548.002 · 9 related

Detection content is published as a reviewed draft. Tune thresholds and exclusions against your own telemetry before enabling this rule for alerting.

windows-cmstp-uac-bypass-attempt-via-autoelevate-com-object-dllhost-execution-4b60e6f2

title: Windows CMSTP UAC Bypass Attempt via Autoelevate COM Object DllHost Execution
id: 67f575f2-fb8f-440c-b039-afffbd34f608
status: stable
description: This rule flags process creation events where the parent process is DllHost.exe with command lines that include specific COM Processid values tied to CMSTP-enabled autoelevate COM objects. UAC bypass techniques matter because they aim to obtain elevated execution without prompting the user. The detection relies on process creation telemetry, focusing on the parent image and parent command-line content plus high/system integrity levels.
references:
  - https://web.archive.org/web/20190720093911/http://www.endurant.io/cmstp/detecting-cmstp-enabled-code-execution-and-uac-bypass-with-sysmon/
  - https://twitter.com/hFireF0X/status/897640081053364225
  - https://medium.com/falconforce/falconfriday-detecting-uac-bypasses-0xff16-86c2a9107abf
  - https://github.com/hfiref0x/UACME
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/process_creation/proc_creation_win_uac_bypass_cmstp_com_object_access.yml
author: Nik Seetharaman, Christian Burkard (Nextron Systems), Huntrule Team
date: 2019-07-31
modified: 2024-12-01
tags:
  - attack.execution
  - attack.privilege-escalation
  - attack.stealth
  - attack.t1548.002
  - attack.t1218.003
  - attack.g0069
  - car.2019-04-001
logsource:
  category: process_creation
  product: windows
detection:
  selection:
    ParentImage|endswith: \DllHost.exe
    ParentCommandLine|contains:
      - " /Processid:{3E5FC7F9-9A51-4367-9063-A120244FBEC7}"
      - " /Processid:{3E000D72-A845-4CD9-BD83-80C07C3B881F}"
      - " /Processid:{BD54C901-076B-434E-B6C7-17C531F4AB41}"
      - " /Processid:{D2E7041B-2927-42FB-8E9F-7CE93B6DC937}"
      - " /Processid:{E9495B87-D950-4AB5-87A5-FF6D70BF3E90}"
    IntegrityLevel:
      - High
      - System
      - S-1-16-16384
      - S-1-16-12288
  condition: selection
falsepositives:
  - Legitimate CMSTP use (unlikely in modern enterprise environments)
level: high
license: DRL-1.1
related:
  - id: 4b60e6f2-bf39-47b4-b4ea-398e33cfe253
    type: derived

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