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Published by CyberDudeBivash • Date: Oct 31, 2025 (IST)

Is Your PC Safe? New Windows LNK 0-Day Flaw Allows Hackers to Attack via Simple Shortcut Files.

A newly documented zero-day vulnerability in Microsoft Windows, tracked as ZDI‑CAN‑25373, lets attackers craft malicious .LNK (shortcut) files that when viewed can execute hidden malicious commands — **no explicit user click required beyond opening/examining the file**.CyberDudeBivash Ecosystem:Apps & Services · Threat Intel · CryptoBivash · News Portal · Subscribe: ThreatWire

TL;DR — Immediate Action Required

What: Windows .lnk shortcut vulnerability ZDI-CAN-25373 abused in the wild since 2017 by 11+ state-sponsored groups.
Risk: Opening or even viewing a malicious shortcut may lead to hidden command execution under your user account—potential full compromise.
Action: Block incoming .lnk files at email/gateway, add hunts for unusual command lines launched from explorer.exe or shortcut refs, ensure OS/MSRC updates applied, restrict user rights.

What the Flaw Is & How It Works

The vulnerability resides in how Windows processes shortcut (.LNK) files, specifically in the handling of command-line arguments hidden within the link target or icon reference. An attacker creates a crafted .LNK file, mails or drops it, the user previews or opens it, and arbitrary commands execute under the user’s context.

Because .LNK files are considered “safe” by many filters and email gateways, they often bypass standard attachment controls.

Who’s Attacking & Why

Research by Trend Micro/ZDI shows this flaw has been used by at least 11 nation-state or state-linked actors (North Korea, Iran, China, Russia) across sectors including government, finance, energy and telecom.

Attackers favour this vector because: it’s easy to distribute (phishing .zip with .lnk inside), often runs under user context so EDR can be bypassed, and looks benign at first glance.

Detection & Hunt Guide

Endpoint / EDR

Look for processes launched by explorer.exe or cdlhost.exe that execute unusual commands or start cmd.exe, powershell.exe with arguments containing /c or .
Track creation of shortcut files (*.lnk) in suspicious folders (Downloads, Email Attachments) and their execution chains.
Monitor for unusual file open events of .lnk files followed by persistence or payload drops.

Email / Gateway

Block or quarantine attachments with .LNK extension or .ZIP containing .LNK.
Flag preview actions on .lnk attachments—alert if .lnk is accessed/viewed then followed by code execution.

Mitigation & Patch Plan

Ensure Windows is fully patched; check for advisories referencing ZDI-CAN-25373. Vendor patch may still be pending — treat as active exploit.
Restrict user rights: run users as standard (non-admin) accounts; avoid auto-elevations.
Disable execution of .LNK files in likely vectors (Downloads, Email attachments) via AppLocker/WDAC policy.
Implement gateway filtering for .lnk and nested .zip containing .lnk files.

Endpoint Hardening Checklist

Enable Forced Restricted Mode in Outlook/Windows so attachments including .lnk are opened in sandbox.
Deploy EDR rule: “ShortCut file launched outside of StartMenu/desktop” → alert.
Apply “least privilege” policy: disable autorun, prevent execution from Downloads folder unless whitelisted.
User awareness: train users not to open shortcuts received by email or from unknown sources.

FAQ

Is this already being exploited?

Yes. Trend ZDI reports nearly 1,000 malicious .lnk exploit samples and confirmed state-actors using this since 2017.

Does this require admin privileges?

No. It executes in the context of the user opening or previewing the .lnk file. If the user is admin, risk is much higher.

Has Microsoft issued a patch?

As of now a full vendor patch is not publicly confirmed; treat this as live active threat.

Sources

Trend Micro / ZDI — “Windows Shortcut Exploit Abused as Zero-Day in Widespread APT Campaigns.”
Ikarus Security — “Zero-Day Vulnerability in Windows Shortcuts (LNK).”
The Hacker News — “Unpatched Windows Zero-Day Flaw Exploited by 11 State-Sponsored Threat Groups”.
CyberScoop — “11 nation-state groups exploit unpatched Microsoft zero-day”.
Guardian Digital — “Why Malicious LNK Files Bypass Email Security Filters”.

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