Introduction
Attackers with access to Zyxel DX3300-T0 and similar network devices can execute arbitrary operating system commands if they obtain valid credentials. This vulnerability impacts a wide range of Zyxel CPE, ONT, and wireless extender models used by service providers and enterprises, making it a significant concern for organizations relying on these devices for network connectivity and management.
About Zyxel: Zyxel is a major international vendor in the networking industry, supplying broadband gateways, CPE, ONTs, and wireless solutions to ISPs, enterprises, and small businesses. Their devices are widely deployed globally, especially in service provider environments, and are known for supporting TR-069 remote management and mesh networking features. Security issues in Zyxel products can have broad operational impact due to their large installed base and integration in critical network infrastructure.
Technical Information
CVE-2025-8693 is a post-authentication OS command injection vulnerability in the web management interface of Zyxel DX3300-T0 and related models. The vulnerability resides in the handling of the priv parameter by a CGI program. When an authenticated user submits a specially crafted HTTP request containing shell metacharacters in the priv parameter, the device firmware passes this input directly to an OS command execution function without adequate sanitization. This enables the attacker to execute arbitrary commands with the privileges of the web server process.
The root cause is improper input validation: the firmware fails to neutralize special elements in user input (CWE-78), allowing command injection. Exploitation requires valid administrative credentials and access to the device's management interface, which is typically restricted to the LAN by default. Attackers can leverage compromised or weak credentials to exploit the flaw, send malicious requests, and gain OS-level access to the device. No public code or proof of concept has been released in advisories.
Patch Information
Zyxel has addressed the vulnerabilities by releasing firmware updates for the affected devices. These updates include patches that rectify the issues by implementing proper input validation and resource management mechanisms. Users are strongly advised to upgrade their devices to the latest firmware versions to mitigate the risks associated with these vulnerabilities. The specific firmware versions containing the fixes are detailed in Zyxel's official security advisory.
Reference: Zyxel Security Advisory - 2025-11-18
Affected Systems and Versions
- Zyxel DX3300-T0 firmware version 5.50(ABVY.6.3)C0 and earlier
- Other affected models include PM3100-T0, PM5100-T0, PM7300-T0, PM7500-00, PX5301-T0, WX3100-T0, WX3401-B0, WX3401-B1, WX5600-T0, WX5610-B0, WE3300-00, and SCR 50AXE, with various firmware versions as listed in the official advisory
- Vulnerable configurations are those running unpatched firmware with web management interface accessible to authenticated users
Vendor Security History
Zyxel has a history of recurring OS command injection vulnerabilities and related issues in its product lines. Previous CVEs include:
- CVE-2024-7261 (critical OS command injection in access points)
- CVE-2024-40891 (unpatched telnet command injection in CPE devices)
- CVE-2022-30525 (OS command injection in firewall products)
The vendor typically issues advisories and patches but sometimes requires direct contact for patch distribution, which can delay remediation. The recurrence of similar vulnerabilities suggests ongoing challenges in secure development and input validation across Zyxel's firmware platforms.
