Windows UAC bypass using NTFS reparse point to place a hijack DLL in Temp

Alerts on file events pointing to a Temp legacy kernel32 DLL within user AppData, consistent with UAC bypass via reparse/DLL targeting.

FreeReviewedSigma · High · v2

Product: windows
Category: file_event
Author: Christian Burkard (Nextron Systems) (SigmaHQ), DRL 1.1
Published: 2021-08-30
Updated: 2026-07-31

Analysis Detection

ATT&CK techniques

Priv Esc → Defense Evasion

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

What it detects

This rule flags file events where an attacker attempts to drop a specific DLL into the per-user temporary AppData path, matching the NTFS reparse point UAC-bypass staging pattern. Such behavior can enable wusa.exe DLL hijacking to run attacker-controlled code with elevated privileges. It relies on file telemetry that records the target filename path, specifically under C:\Users\ and ending with the referenced DLL name in the Local\Temp directory.

Reporting behind it

Related detections9 linkedT1548.002 — drag to rearrange

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Suspicious UAC Bypass via COMAutoApprovalList Registry Modification (via registry_set)

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Windows UAC bypass using NTFS reparse point to place a hijack DLL in Temp

Pivot detection · T1548.002 · 9 related

Changelog

v2
Candidate ingested via manual entry.2026-07-31
v1
No changelog recorded for this version.2026-07-30

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

windows-uac-bypass-attempt-via-ntfs-reparse-point-targeting-temp-dll-path-7fff6773

title: Windows UAC bypass using NTFS reparse point to place a hijack DLL in Temp
id: 2a0047ff-a9cb-4110-9c93-9bb807af53fb
status: test
description: This rule flags file events where an attacker attempts to drop a specific DLL into the per-user temporary AppData path, matching the NTFS reparse point UAC-bypass staging pattern. Such behavior can enable wusa.exe DLL hijacking to run attacker-controlled code with elevated privileges. It relies on file telemetry that records the target filename path, specifically under C:\Users\ and ending with the referenced DLL name in the Local\Temp directory.
references:
  - https://github.com/hfiref0x/UACME
  - https://github.com/SigmaHQ/sigma/blob/master/rules/windows/file/file_event/file_event_win_uac_bypass_ntfs_reparse_point.yml
author: Christian Burkard (Nextron Systems), Huntrule Team
date: 2021-08-30
modified: 2022-10-09
tags:
  - attack.privilege-escalation
  - attack.t1548.002
logsource:
  category: file_event
  product: windows
detection:
  selection:
    TargetFilename|startswith: C:\Users\
    TargetFilename|endswith: \AppData\Local\Temp\api-ms-win-core-kernel32-legacy-l1.DLL
  condition: selection
falsepositives:
  - Unknown
level: high
license: DRL-1.1
related:
  - id: 7fff6773-2baa-46de-a24a-b6eec1aba2d1
    type: derived

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