Microsoft Windows Internet Shortcut Files SmartScreen Bypass
CVE-2024-21412 is a Microsoft Windows Internet Shortcut Files security feature bypass vulnerability affecting handling of specially crafted .url shortcut files. The provided content consistently describes the flaw as enabling bypass of Microsoft Defender SmartScreen / Mark-of-the-Web-style security warnings when a user opens or clicks a malicious Internet Shortcut file. Reported exploitation chains used .url files that referenced attacker-controlled remote content over WebDAV, SMB, or UNC paths, including cases where one .url pointed to another remote .url or to script content such as .vbs, .bat, .cmd, or .js. Multiple sources in the content characterize the issue as related to or a bypass of the earlier CVE-2023-36025 protections. In observed campaigns, attackers used phishing lures and fake document or image themes to induce users to open the shortcut, after which Windows Explorer / Internet Shortcut handling could retrieve and execute the next-stage payload without the expected SmartScreen warning flow.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
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
25 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.