CMSTP UAC Bypass via COM Object Access

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

Detects UAC Bypass Attempt Using Microsoft Connection Manager Profile Installer Autoelevate-capable COM Objects (e.g. UACMe ID of 41, 43, 58 or 65)

MITRE ATT&CK coverage

Tactic	Techniques
Privilege Escalation	`T1548.002` Abuse Elevation Control Mechanism: Bypass User Account Control
Stealth	`T1218.003` System Binary Proxy Execution: CMSTP

Event coverage

Provider	Event	Title
Sysmon	Event ID 1	Process creation

Rule body yaml

title: CMSTP UAC Bypass via COM Object Access
id: 4b60e6f2-bf39-47b4-b4ea-398e33cfe253
status: stable
description: Detects UAC Bypass Attempt Using Microsoft Connection Manager Profile Installer Autoelevate-capable COM Objects (e.g. UACMe ID of 41, 43, 58 or 65)
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
author: Nik Seetharaman, Christian Burkard (Nextron Systems)
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}' # cmstplua.dll
            - ' /Processid:{3E000D72-A845-4CD9-BD83-80C07C3B881F}' # CMLUAUTIL
            - ' /Processid:{BD54C901-076B-434E-B6C7-17C531F4AB41}' # EditionUpgradeManagerObj.dll
            - ' /Processid:{D2E7041B-2927-42FB-8E9F-7CE93B6DC937}' # colorui.dll
            - ' /Processid:{E9495B87-D950-4AB5-87A5-FF6D70BF3E90}' # wscui.cpl
        IntegrityLevel:
            - 'High'
            - 'System'
            - 'S-1-16-16384' # System
            - 'S-1-16-12288' # High
    condition: selection
falsepositives:
    - Legitimate CMSTP use (unlikely in modern enterprise environments)
level: high

Stages and Predicates

Stage 0: `condition`

selection

Stage 1: `selection`

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'

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`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 29 (sigma 22, splunk 4, elastic 3) `System` corpus 29 (sigma 22, splunk 4, elastic 3)
`ParentCommandLine`	match	`/Processid:{3E000D72-A845-4CD9-BD83-80C07C3B881F}` `/Processid:{3E5FC7F9-9A51-4367-9063-A120244FBEC7}` `/Processid:{BD54C901-076B-434E-B6C7-17C531F4AB41}` `/Processid:{D2E7041B-2927-42FB-8E9F-7CE93B6DC937}` `/Processid:{E9495B87-D950-4AB5-87A5-FF6D70BF3E90}`
`ParentImage`	ends_with	`\DllHost.exe` corpus 7 (sigma 7)

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

CMSTP UAC Bypass via COM Object Access

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Indicators

Keyboard shortcuts

Search operators

CMSTP UAC Bypass via COM Object Access

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Indicators

Stage 0: `condition`

Stage 1: `selection`