Chinese Hackers Exploit Cityworks 0-Day to Hit US Local Governments

Cisco Talos warns of active exploitation of a zero-day vulnerability (CVE-2025-0994) in Cityworks supposedly by Chinese hackers from the UAT-6382 threat group. Learn about the malware, affected organizations, and critical security patches.

Cisco Talos researchers have issued a critical alert regarding active cyberattacks targeting Trimble Cityworks, a widely used platform for managing public assets. According to Cisco Talos’ latest research, shared with Hackread.com, a sophisticated threat group, tracked as UAT-6382, is exploiting a newly discovered high-severity vulnerability CVE-2025-0994 in the system.

This vulnerability, having a CVSS score of 8.6, allows for remote code execution, meaning attackers can run their malicious programs on affected systems from afar. These attacks have been observed since January 2025 and primarily target local government organizations in the United States. Some attacks have already resulted in successful compromises.

The Cybersecurity and Infrastructure Security Agency (CISA) and Trimble have also released their warnings about this serious flaw. Reportedly, the vulnerability allows attackers to gain remote access and execute malicious code against Microsoft Internet Information Services web server without needing to authenticate. Cityworks vulnerability affects versions before 15.8.9 and Cityworks with Office Companion versions before 23.10.

Once inside, UAT-6382 quickly deploys web shells like AntSword and chinatso/Chopper on the compromised web servers to maintain hidden access. They also use custom-made tools, including a Rust-based loader called TetraLoader to install more persistent malware such as Cobalt Strike and VSHell.

“Talos has found intrusions in enterprise networks of local governing bodies in the United States (U.S.), beginning in January 2025 when initial exploitation first took place. UAT-6382 successfully exploited CVE-2025-0944, conducted reconnaissance and rapidly deployed a variety of web shells and custom-made malware to maintain long-term access.”

Cisco Talos

****Chinese-Speaking Actors Identified****

Based on their methods and tools, Cisco Talos’ report suggests with high confidence that UAT-6382 is a group of “Chinese-speaking threat actors.” Evidence supporting this includes the Chinese language found in the web shells and the fact that MaLoader, the framework used to build TetraLoader, is also written in Simplified Chinese. This malware builder, which emerged in December 2024, allows operators to package malicious code into Rust-based programs like TetraLoader.

MaLoader Builder Interface (Source: Cisco Talos)

Researchers noted that upon gaining access, the attackers show a particular interest in systems related to utility management. Their initial actions involve scanning the compromised server to understand its setup, looking for specific directories related to Cityworks, and then quickly setting up their web shells. They also stage sensitive files for potential data theft and deploy backdoors using PowerShell commands to ensure long-term access.

****Understanding the Malware****

TetraLoader’s main function is to inject various payloads into legitimate processes, such as notepad.exe. These payloads can be Cobalt Strike beacons, which are widely used by attackers for command and control, or VShell stagers.

For your information, VShell is a GoLang-based remote access Trojan that allows attackers to manage files, run commands, take screenshots, and set up proxy services on infected systems. Like other tools used by this group, the VShell control panels also display Chinese text, indicating the operators’ proficiency in the language.

Cityworks has released security patches to address the CVE-2025-0994 vulnerability, urging users to update immediately. Organizations should monitor suspicious activity using Cisco Talos’ technical indicators of compromise (IOCs). Cisco Talos also recommend the use of security products like Cisco Secure Endpoint, Secure Firewall, and Umbrella to protect against such attacks.