Chinese hackers target European diplomats with Windows zero-day flaw

• Mustang Panda used CVE-2025-9491 to target European diplomats via phishing and malicious .LNK files
• Exploited Windows Shell Link flaw deploys PlugX RAT for persistent access and data exfiltration
• Hundreds of samples link the zero-day to long-running Chinese espionage campaigns since at least 2017

Chinese state-sponsored threat actors have been abusing a Windows zero-day vulnerability to target diplomats across the European continent, security researchers are warning.

Security researchers Arctic Wolf Labs recently said they observed a nation-state actor known as Mustang Panda (UNC6384) sending out spear-phishing emails to diplomats in Hungary, Belgium, Serbia, Italy, and the Netherlands.

Curiously enough, among the victims are Hungary and Serbia, two countries who have strong ties with China and are, in many things, considered Chinese allies and partners - although in August 2025 it was revealed that China was spying on yet another major ally - Russia.

Abusing .LNK files

The phishing emails were themed around NATO defense procurement workshops, European Commission border facilitation meetings, and other similar diplomatic events, the researchers explained.

These carried a malicious .LNK file which, through the abuse of CVE-2025-9491, was built to deploy a Remote Access Trojan (RAT) called PlugX. This RAT gives its operators persistent access to the compromised system, as well as the ability to eavesdrop on communication, exfiltrate files, and more.

The bug stems from the way Windows handles shortcut files and is described as a UI misrepresentation issue in the Shell Link mechanism. It lets a crafted .LNK file hide the real command line so a different, malicious command runs when the user runs, or previews, the shortcut.

Since exploitation requires user interaction, the bug was given a relatively low severity score of 7.8/10 (high). Still, researchers found hundreds (possibly even thousands) of .LNK samples, tying the flaw to long-running espionage campaigns, with some examples dating back to 2017.

"Arctic Wolf Labs assesses with high confidence that this campaign is attributable to UNC6384, a Chinese-affiliated cyber espionage threat actor," the researchers said.

"This attribution is based on multiple converging lines of evidence including malware tooling, tactical procedures, targeting alignment, and infrastructure overlaps with previously documented UNC6384 operations."

Via BleepingComputer

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