Potential Notepad++ CVE-2025-49144 Exploitation

Status: experimental
Severity: high
Log source: category process_creation, product windows
Author: Swachchhanda Shrawan Poudel (Nextron Systems)
Source: github.com/SigmaHQ/sigma

Detects potential exploitation of CVE-2025-49144, a local privilege escalation vulnerability in Notepad++ installers (v8.8.1 and prior) where the installer calls regsvr32.exe without specifying the full path. This allows an attacker to execute arbitrary code with elevated privileges by placing a malicious regsvr32.exe alongside this Legitimate Notepad++ installer. The vulnerability is triggered when the installer attempts to register the NppShell.dll file, which is a component of Notepad++.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1574.008` Hijack Execution Flow: Path Interception by Search Order Hijacking
Stealth	`T1574.008` Hijack Execution Flow: Path Interception by Search Order Hijacking

Telemetry coverage

Provider	Record / event type
Sysmon	Event ID 1: Process creation
Security-Auditing	Event ID 4688: A new process has been created.

Rule body

title: Potential Notepad++ CVE-2025-49144 Exploitation
id: 933f0bb5-0681-4fe7-8a17-4e6cccbaac44
status: experimental
description: |
    Detects potential exploitation of CVE-2025-49144, a local privilege escalation vulnerability in Notepad++ installers (v8.8.1 and prior) where the installer calls regsvr32.exe without specifying the full path.
    This allows an attacker to execute arbitrary code with elevated privileges by placing a malicious regsvr32.exe alongside this Legitimate Notepad++ installer.
    The vulnerability is triggered when the installer attempts to register the NppShell.dll file, which is a component of Notepad++.
references:
    - https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2025-49144
    - https://x.com/NullSecurityX/status/1937444064867029179
author: Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2025-06-26
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.execution
    - attack.stealth
    - attack.t1574.008
    - cve.2025-49144
    - detection.emerging-threats
logsource:
    product: windows
    category: process_creation
detection:
    selection:
        Image|endswith: '\regsvr32.exe'
        CommandLine|startswith: 'regsvr32 /s'
        CommandLine|contains: '\contextMenu\NppShell.dll'
    filter_main_legit_regsvr32:
        Image:
            - 'C:\Windows\System32\regsvr32.exe'
            - 'C:\Windows\SysWOW64\regsvr32.exe'
    condition: selection and not 1 of filter_main_*
falsepositives:
    - Unknown
level: high

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_*

Stage 1: `selection`

selection:
    Image|endswith: '\regsvr32.exe'
    CommandLine|startswith: 'regsvr32 /s'
    CommandLine|contains: '\contextMenu\NppShell.dll'

Stage 2: `not filter_main_legit_regsvr32`

filter_main_legit_regsvr32:
    Image:
        - 'C:\Windows\System32\regsvr32.exe'
        - 'C:\Windows\SysWOW64\regsvr32.exe'

Exclusions

The rule actively suppresses these predicates.

Field	Kind	Excluded values	Search
`Image`	eq	`C:\Windows\SysWOW64\regsvr32.exe`	`excludes:Image` `field:"Image" value:"C:\Windows\SysWOW64\regsvr32.exe"`
`Image`	eq	`C:\Windows\System32\regsvr32.exe`	`excludes:Image` `field:"Image" value:"C:\Windows\System32\regsvr32.exe"`

Indicators

These rows show field, operator, and value matches.

Field	Kind	Values	Search
`CommandLine`	match	`\contextMenu\NppShell.dll`	`field:"CommandLine" kind:match value:"\contextMenu\NppShell.dll"`
`CommandLine`	starts_with	`regsvr32 /s`	`field:"CommandLine" kind:starts_with value:"regsvr32 /s"`
`Image`	ends_with	`\regsvr32.exe` corpus 64 (sigma 64)	`field:"Image" kind:ends_with value:"\regsvr32.exe"`