UAC Bypass Abusing Winsat Path Parsing - Process

Status: test
Severity: high
Log source: category process_creation, product windows
Author: Christian Burkard (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects the pattern of UAC Bypass using a path parsing issue in winsat.exe (UACMe 52)

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548.002` Abuse Elevation Control Mechanism: Bypass User Account Control

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation

Rule body

title: UAC Bypass Abusing Winsat Path Parsing - Process
id: 7a01183d-71a2-46ad-ad5c-acd989ac1793
status: test
description: Detects the pattern of UAC Bypass using a path parsing issue in winsat.exe (UACMe 52)
references:
    - https://github.com/hfiref0x/UACME
author: Christian Burkard (Nextron Systems)
date: 2021-08-30
modified: 2024-12-01
tags:
    - attack.privilege-escalation
    - attack.t1548.002
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        IntegrityLevel:
            - 'High'
            - 'System'
            - 'S-1-16-16384' # System
            - 'S-1-16-12288' # High
        ParentImage|endswith: '\AppData\Local\Temp\system32\winsat.exe'
        ParentCommandLine|contains: 'C:\Windows \system32\winsat.exe'
    condition: selection
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

selection:
    IntegrityLevel:
        - 'High'
        - 'System'
        - 'S-1-16-16384'
        - 'S-1-16-12288'
    ParentImage|endswith: '\AppData\Local\Temp\system32\winsat.exe'
    ParentCommandLine|contains: 'C:\Windows \system32\winsat.exe'

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`IntegrityLevel`	eq	`High` corpus 21 (sigma 17, kusto 3, splunk 1) `S-1-16-12288` corpus 21 (sigma 17, kusto 3, splunk 1) `S-1-16-16384` corpus 30 (sigma 22, splunk 4, elastic 3, kusto 1) `System` corpus 30 (sigma 22, splunk 4, elastic 3, kusto 1)	`field:"IntegrityLevel" kind:eq`
`ParentCommandLine`	match	`C:\Windows \system32\winsat.exe`	`field:"ParentCommandLine" kind:match value:"C:\Windows \system32\winsat.exe"`
`ParentImage`	ends_with	`\AppData\Local\Temp\system32\winsat.exe`	`field:"ParentImage" kind:ends_with value:"\AppData\Local\Temp\system32\winsat.exe"`

UAC Bypass Abusing Winsat Path Parsing - Process

MITRE ATT&CK coverage

Telemetry coverage

Rule body

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`