Microsoft has recently released a micropatch for CVE-2025-9491, a critical vulnerability in Windows Shortcut (LNK) files. Trend Micro’s Zero Day Initiative (ZDI) was the first to publicly disclose this vulnerability back in March 2025. It gives attackers a way to weaponize the way command-line arguments are displayed in LNK files. This vulnerability currently has a severity rating of 7.8 – high – on the Common Vulnerability Scoring System (CVSS). It thus represents a serious remote code execution threat.
State-sponsored clusters originating from China, Iran, North Korea, and most notably Russia have all been identified in CVE-2025-9491 exploitation. This vulnerability creates a serious vector for data theft, espionage, and financially motivated campaigns. Attacks to exploit this vulnerability go back to as early as 2017, making it a long-standing issue that is finally being addressed by Microsoft.
Details of the Vulnerability
CVE-2025-9491 focuses on the way Windows parses LNK files, particularly with regard to how command-line arguments may be displayed to the user. An attacker can simply craft an LNK file that runs a 260+ character command. To the user, this manipulation obfuscates all but the first 260 characters of that URL. A malicious actor can do all of the above and conceal harmful or hateful content within the file. This insidious strategy further prevents users from being able to identify risks.
According to the National Institute of Standards and Technology (NIST) National Vulnerability Database (NVD), “The specific flaw exists within the handling of .LNK files.” As they elaborate, if an attacker opens a .LNK file in the Windows GUI, carefully designed data can obscure dangerous information. This is concerning, because users will be unable to identify harmful content hidden in the document. This flaw allows malicious actors to run arbitrary code within the current user’s context.
As Microsoft emphasizes, “due to the user interaction involved and the fact that the system already warns users that this format is untrusted,” users are urged to exercise caution when dealing with unknown files.
Recent Exploitation Attempts
In late October 2025, Arctic Wolf detected an offensive campaign using CVE-2025-9491. Reports have suggested that Chinese state threat actors used this vulnerability in attacks against European diplomatic and governmental establishments. These breaches targeted stealing sensitive employee information and deploying malware like PlugX.
The damage that the ongoing risk of CVE-2025-9491 is causing today highlights the need for robust cybersecurity protections. With 11 federally funded field offices currently taking advantage of this loophole, it is important to stay on guard organizations and citizens alike.
“Even though malicious shortcuts could be constructed with fewer than 260 characters, we believe disrupting actual attacks detected in the wild can make a big difference for those targeted.” – Source not specified
Mitigation Efforts and Recommendations
In reaction to this major risk, Microsoft has released a micropatch that makes users much safer by doing so. And now, when users attempt to open an LNK file, this micropatch proactively protects them right away. It triggers only if the file’s command-line arguments are more than 260 characters. By padding the Target field of the LNK file, this protection seeks to prevent possible exploitation from CVE-2025-9491.
A Microsoft spokesperson stated, “As a security best practice, Microsoft encourages customers to exercise caution when downloading files from unknown sources as indicated in security warnings, which have been designed to recognize and warn users about potentially harmful files.” This forward-looking stance underscores the importance of keeping users on the lookout for cybersecurity threats.
The release of this micropatch demonstrates that Microsoft is willing to be proactive in fixing vulnerabilities and protecting user safety and security. Security is top of mind for organizations today. Advocates will need to continue to be on guard and be ready to counter new threats that arise.
