Windows Internet Shortcut Files SmartScreen Security Feature Bypass
CVE-2024-21412 is a Microsoft Windows Internet Shortcut Files security feature bypass vulnerability affecting the handling of specially crafted .url Internet Shortcut files. The flaw allows an unauthenticated attacker to send or host a crafted shortcut file such that, when a user opens or clicks it, Windows/Defender SmartScreen security checks and warning prompts can be bypassed. Reporting cited in the provided content indicates the issue was exploited using Internet Shortcut files that referenced remote content, including chains where a .url pointed to another .url or to attacker-controlled content on a remote SMB/WebDAV location, resulting in execution of the next-stage payload without the expected SmartScreen warning. Multiple sources in the content describe it as a bypass related to the earlier CVE-2023-36025 behavior and note in-the-wild exploitation by Water Hydra/DarkCasino and in DarkGate campaigns.
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Impact, mitigation & remediation
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Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository demonstrates a proof-of-concept exploit for CVE-2024-21412, targeting Microsoft Windows. The exploit leverages a chain of .url (Internet Shortcut) files and a crafted HTML file to bypass Microsoft Defender SmartScreen and achieve arbitrary code execution via a remote SMB share. The structure includes: - A 'webserver' directory with an HTML file that uses the 'search:' protocol to direct Windows Explorer to a malicious SMB share. - A 'samba-compose' directory with Docker Compose and Samba configuration files, setting up an SMB server with specific shares and user credentials. - The 'pictures' subdirectory contains chained .url files that ultimately point to a CMD script (a2.cmd) inside a ZIP archive on the SMB share. - The 'loader' directory contains the CMD script payload, which demonstrates code execution by launching calc.exe. Commented lines in the script suggest the potential for more advanced payloads, such as DLL injection. The exploit requires the attacker to run both the web server and the Samba server, and the victim to access the malicious HTML or .url files, triggering the exploit chain. The endpoints and configuration files are tailored for a local network (192.168.1.70), but could be adapted for other environments. The repository is a functional POC and does not include weaponized or highly automated payloads.
Affected products & vendors
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Recent activity
22 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A SmartScreen/Mark-of-the-Web bypass vulnerability historically associated in the report with WaterHydra activity; noted as patched by Microsoft in February 2024.
A Windows SmartScreen zero-day / Mark-of-the-Web bypass exploited by WaterHydra/DarkCasino in late 2023 and patched by Microsoft in February 2024.
A vulnerability referenced as affecting Internet Shortcut Files security; discussed as one of the exploited vulnerabilities used by FishMonger (aka Earth Lusca).
A Microsoft vulnerability that CISA KEV’s knownRansomwareCampaignUse field silently flipped to Known during 2025 (evidence of ransomware campaign use).
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.