Rule Document 1:301398

Rule Category

OS-WINDOWS -- Snort has detected traffic targeting vulnerabilities in a Windows-based operating system. This does not include browser traffic or other software on the OS, but attacks against the OS itself. (such as?)

Alert Message

OS-WINDOWS Microsoft Windows security feature bypass attempt

Rule Explanation

This rule looks for specially crafted files intended to exploit a Windows Shell security feature bypass vulnerability.

What To Look For

This rule fires on attempts to exploit a security feature bypass vulnerability in Windows.

Known Usage

Attacks/Scans seen in the wild

False Positives

No known false positives

Contributors

Cisco Talos Intelligence Group

Rule Groups

MITRE::ATT&CK Framework::Enterprise::Execution::User Execution::Malicious File

An adversary may rely upon a user opening a malicious file in order to gain execution. Users may be subjected to social engineering to get them to open a file that will lead to code execution. This user action will typically be observed as follow-on behavior from Spearphishing Attachment. Adversaries may use several types of files that require a user to execute them, including .doc, .pdf, .xls, .rtf, .scr, .exe, .lnk, .pif, and .cpl.

Rule Categories::Operating Systems::Windows

Rule Categories::File::Office

MITRE::ATT&CK Framework::Enterprise::Initial Access::Drive-by Compromise

CVE

CVE-2026-21510

Additional Links

msrc.microsoft.com/update-guide/vulnerability/CVE-2026-21510

Rule Vulnerability

Remote File Inclusion

Remote File Inclusion (RFI) attacks occur when a webserver takes a file crafted by an attacker as input and runs or stores it in an unsafe manner. For instance, the webserver could accept an image file that is actually code, then call it to execute after uploading. RFI attacks happen on web applications that dynamically include external files or scripts. A successful RFI can lead to data leaks, remote code execution, or cross site scripting. Avoid dynamic inclusion of user input files, or whitelist files that may be included. Keep the PHP allow_url_include option set to off; this will not protect against Local File Inclusion attacks.

CVE Additional Information

This product uses data from the NVD API but is not endorsed or certified by the NVD.

CVE-2026-21510

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