) use NSSM 2.24 to run their background processes as Windows services. The Vulnerability : During installation, these apps often place in a folder where the "Everyone" or "Users" group has permissions. The Exploit A low-privileged user identifies that the binary is writable. They replace the legitimate
The underlying weakness is the lack of authentication for a critical function. The product does not perform any authentication for functionality that requires a provable user identity or consumes a significant amount of resources. A vulnerability with such characteristics has broad implications for any system where an NSSM‑based service is installed with lax permissions—a scenario that is by no means limited to Phoenix Contact software.
This vulnerability was initially identified in the installer, which bundles a copy of nssm.exe as part of the DAUM‑WINDOWS‑SERVICE. During installation, the file permissions on nssm.exe were not properly secured. Because of this misconfiguration, a low‑privileged local attacker can replace the legitimate nssm.exe with a malicious executable. When the corresponding Windows service (running with high privileges) is later restarted or the system reboots, the attacker’s code executes with administrative rights, granting full control over the compromised machine. nssm-2.24 exploit
The Non‑Sucking Service Manager (NSSM) is a popular open‑source tool that allows system administrators to run almost any executable as a Windows service, complete with process monitoring and automatic restart capabilities. It is often praised as a powerful and lightweight alternative to the built‑in Windows Service Control Manager. However, a tool designed for convenience can also become a weapon when misused. This article takes a comprehensive look at the security concerns surrounding NSSM, with a particular focus on version 2.24, the vulnerabilities that have been identified, and the various ways attackers have exploited this utility in real‑world campaigns.
The vulnerability is triggered when an attacker sends a specially crafted request to the NSSM service, which then executes the request with elevated privileges. This allows the attacker to execute arbitrary code on the system, potentially leading to a complete compromise of the system. ) use NSSM 2
The nssm-2.24 exploit typically involves the following steps:
Regularly update NSSM and related software to ensure you are running versions without known vulnerabilities. They replace the legitimate The underlying weakness is
Exploit code for CVE-2016-20033 is publicly available on platforms including Exploit-DB and Zero Science, though active exploitation in the wild remains unconfirmed.
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While not an exploit target, NSSM is used as a post-exploitation tool to ensure malicious code remains running: Persistence Mechanism
