Potential CVE-2026-33829 Exploitation - Windows Snipping Tool Remote File Path URI

SIGMA detection rule by Samir Bousseaden, Swachchhanda Shrawan Poudel (Nextron Systems) · NOASSERTION

Detects potential exploitation of CVE-2026-33829, a vulnerability in the Windows Snipping Tool URI handler (ms-screensketch:). An attacker can abuse the 'filePath' parameter to supply a UNC path or HTTP URL, causing SnippingTool.exe to initiate a connection to a remote resource. When a UNC path is used (e.g. \\attacker.com\share), this triggers an outbound NTLM authentication attempt, allowing the attacker to capture or relay the victim's Net-NTLMv2 hash. HTTP-based paths may result in remote file loading or server-side request forgery (SSRF)-style access. The URI can be delivered via a malicious hyperlink, phishing email, or web page.

title: Potential CVE-2026-33829 Exploitation - Windows Snipping Tool Remote File Path URI
id: 7c3a5b1d-9e2f-4a8c-b5d7-1e0f3c6a9b2d
status: test
description: |
    Detects potential exploitation of CVE-2026-33829, a vulnerability in the Windows Snipping Tool URI handler (ms-screensketch:).
    An attacker can abuse the 'filePath' parameter to supply a UNC path or HTTP URL, causing SnippingTool.exe to initiate a connection to a remote resource.
    When a UNC path is used (e.g. \\attacker.com\share), this triggers an outbound NTLM authentication attempt, allowing the attacker to capture or relay the victim's Net-NTLMv2 hash.
    HTTP-based paths may result in remote file loading or server-side request forgery (SSRF)-style access.
    The URI can be delivered via a malicious hyperlink, phishing email, or web page.
references:
    - https://x.com/BlackArrowSec/status/2044374743491424508
    - https://x.com/SBousseaden/status/2044417029721997635
author: Samir Bousseaden, Swachchhanda Shrawan Poudel (Nextron Systems)
date: 2026-04-28
tags:
    - attack.credential-access
    - attack.t1187
    - detection.emerging-threats
    - cve.2026-33829
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\SnippingTool.exe'
        CommandLine|contains:
            # '\\\\'  = literal double backslash (UNC path start); '%5C' and '%%5C' are URL-encoded variations of the same backslash character
            - 'ms-screensketch:edit?&filePath=\\\\'
            - 'ms-screensketch:edit?&filePath=%%5C'
            - 'ms-screensketch:edit?&filePath=%5C'
            - 'ms-screensketch:edit?&filePath=http'
    condition: selection
falsepositives:
    - Unknown
level: high
regression_tests_path: regression_data/rules-emerging-threats/2026/Exploits/CVE-2026-33829/proc_creation_win_exploit_cve_2026_33829/info.yml

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