Windows Shortcut Vulnerability: Critical Threat Exposed

The Windows Shortcut Vulnerability has been exploited by 11 state-sponsored threat actors. Learn how it works and what your teams must do to defend systems.

Table of Contents

1. Overview of the Windows Shortcut Vulnerability
2. TTPs Used in Exploiting ZDI-CAN-25373
3. State-Sponsored Campaigns and Attribution
4. Industries and Geographies Targeted
5. Mitigation and Defense Recommendations
   

Overview of the Windows Shortcut Vulnerability

The Windows Shortcut Vulnerability (ZDI-CAN-25373) has been actively exploited in the wild since at least 2017, with new threat intel confirming operations by 11 state-sponsored APTs. This zero-day flaw affects how Windows parses .lnk (shortcut) files via the Shell32 library, allowing malicious commands to execute without user visibility. Attackers leverage this to perform covert code execution, deploy payloads, and establish persistence across victim networks.

Trend Micro’s Zero Day Initiative (ZDI) flagged nearly 1,000 unique .lnk samples abusing this logic flaw, which Microsoft has not yet formally patched. Despite the longevity of this bug, it has only recently come to public light, revealing years of covert exploitation across defense, finance, and critical infrastructure sectors.

TTPs Used in Exploiting ZDI-CAN-25373

Threat actors craft malicious .lnk files with concealed command-line arguments. By embedding whitespace characters (e.g., spaces, tabs, carriage returns) before command strings in the shortcut’s Target field, adversaries prevent Windows Explorer from displaying the full path. Users unknowingly execute embedded PowerShell or script-based commands, initiating lateral movement or payload staging.

This exploit technique is stealthy due to its non-reliance on dropped executables. The shortcut file alone can initiate a kill chain, making it attractive for low-signal intrusion vectors. Common payloads observed include Cobalt Strike beacons, remote access Trojans (RATs), and custom loaders tailored to the APT group’s objectives.

Notably, this bypasses many endpoint detection systems that rely on execution visibility or behavioral triggers from file-based malware.

State-Sponsored Campaigns and Attribution

ZDI’s report links this vulnerability to activity from 11 state-sponsored actors based in North Korea, China, Iran, and Russia. Over 50% of the detected .lnk samples were attributed to North Korean APTs, many of which share tooling and TTPs across campaigns. This highlights not only active exploitation but also long-term operational use.

Attribution was based on overlaps in command-and-control infrastructure, payload reuse, and consistent usage patterns of .lnk obfuscation techniques. Some actors rotated infrastructure monthly, while others used .lnk vectors as part of supply chain and watering-hole attacks, making this an adaptable tool in the APT arsenal.

This mirrors older techniques used in Stuxnet, Equation Group, and Lazarus Group campaigns—validating that shortcut files remain viable for stealthy access and privilege escalation.

Industries and Geographies Targeted

Victimology analysis reveals a wide swath of sectors targeted, primarily:

• Government & Military
• Financial (Crypto-related particularly)
• Telecommunications
• Energy and Utilities
• Think Tanks and NGOs

Geographically, incidents span North America, Europe, East Asia, South America, and Australia, reflecting strategic intelligence collection objectives. North Korean groups were especially active in attacking blockchain and fintech infrastructure, while Iranian actors focused on regional geopolitical targets.

These campaigns often used .lnk files as initial access vectors, sometimes embedded in zip archives or attached to phishing lures themed around job offers, government notices, or RFP documents.

Mitigation and Defense Recommendations

Despite active exploitation, Microsoft has not yet issued a patch, stating ZDI-CAN-25373 doesn’t meet criteria for immediate servicing. Until then, the cybersecurity community must deploy defense-in-depth approaches to mitigate risk.

Defensive Actions:

• Endpoint Hardening: Prevent execution of .lnk files from external media or untrusted directories via GPO or EDR rules.
• User Awareness: Train employees not to open shortcut files from email attachments or unknown sources.
• Disable Shortcut Parsing (if feasible): Advanced users can disable certain Shell32 features via registry settings, though this may impact usability.
• Monitor Shortcut Metadata: Detect .lnk files with abnormal Target field sizes or padding characters using SIEM tools.
• Threat Hunting: Proactively scan for suspicious .lnk files using YARA rules targeting padding patterns, especially on high-value endpoints.
  

Consider integrating .lnk abuse detection into your MITRE ATT&CK-based threat modeling, under T1204.002: User Execution – Malicious File.

Internal Links

• Server Hardening Tips for Windows Environments
• Advanced Threat Detection Guide
  

External References

• Trend Micro ZDI: Windows Shortcut Vulnerability
• Microsoft: File Explorer Behavior and .lnk Execution
• MITRE ATT&CK – T1204.002: User Execution: Malicious File