CVE-2017-15009 in PRTG Network Monitor
Summary
by MITRE
PRTG Network Monitor version 17.3.33.2830 is vulnerable to reflected Cross-Site Scripting on error.htm (the error page), via the errormsg parameter.
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Analysis
by VulDB Data Team • 11/21/2019
PRTG Network Monitor version 17.3.33.2830 contains a reflected cross-site scripting vulnerability that affects the error handling mechanism of the application. This vulnerability exists within the error.htm page which is responsible for displaying error messages to users when system issues occur. The specific flaw occurs when the application processes the errormsg parameter without proper input sanitization or output encoding, allowing malicious actors to inject arbitrary JavaScript code that will execute in the context of other users' browsers. The vulnerability is classified as a reflected XSS attack because the malicious payload is reflected off the web server back to the victim's browser rather than being stored on the server. This particular vulnerability affects the error handling functionality of the network monitoring system, which is a critical component of the application's user interface. The impact is particularly concerning because network monitoring tools like PRTG are often used in enterprise environments where they may have elevated privileges and access to sensitive network information, making them attractive targets for attackers seeking to exploit such vulnerabilities.
The technical implementation of this vulnerability stems from inadequate input validation and output encoding practices within the error page handling logic. When an error occurs in PRTG Network Monitor, the system generates an error.htm page that displays the errormsg parameter to users. However, the application fails to properly sanitize or encode the user-supplied input before incorporating it into the HTML response. This allows attackers to craft malicious payloads that, when processed by the vulnerable application, get executed in the browsers of unsuspecting users who view the error page. The vulnerability is categorized under CWE-79 as a failure to sanitize user input before including it in output, and more specifically aligns with CWE-798 when considering the exposure of sensitive data through improper error handling. The attack vector requires the victim to be tricked into clicking on a malicious link that contains the crafted XSS payload, making this a client-side exploitation technique that relies on social engineering or direct user interaction with malicious URLs.
The operational impact of this vulnerability extends beyond simple script execution, as it represents a significant security risk for organizations relying on PRTG Network Monitor for critical infrastructure monitoring. An attacker who successfully exploits this vulnerability could potentially execute malicious scripts in the context of authenticated users' browsers, leading to session hijacking, credential theft, or further exploitation of the network monitoring environment. The attack could be particularly damaging in enterprise settings where PRTG is used to monitor critical network infrastructure, as the compromised system could provide attackers with visibility into network operations or enable them to manipulate monitoring data. This vulnerability could also be leveraged as a stepping stone for more sophisticated attacks, potentially allowing attackers to gain access to additional network resources or escalate privileges within the monitored environment. The reflected nature of the XSS means that attackers can craft payloads that are immediately executed without requiring persistent storage on the server, making detection and mitigation more challenging. Organizations using this version of PRTG are particularly vulnerable because the error handling page is likely to be accessed frequently during normal system operations, increasing the attack surface and potential exposure windows.
Mitigation strategies for this vulnerability should focus on immediate remediation through software updates and input validation improvements. The primary solution involves upgrading to a patched version of PRTG Network Monitor that addresses this specific XSS vulnerability in the error handling mechanism. Organizations should also implement proper input sanitization and output encoding practices to ensure that any user-supplied data is properly escaped before being rendered in HTML contexts. Network administrators should consider implementing web application firewalls or security filters that can detect and block suspicious XSS payloads targeting known vulnerable parameters such as errormsg. Additional defensive measures include disabling unnecessary error pages or implementing stricter content security policies that prevent script execution in error contexts. From an ATT&CK perspective, this vulnerability maps to T1059.007 for the execution of scripts and T1566 for the initial compromise through social engineering techniques. Organizations should also review their incident response procedures to ensure they can quickly detect and respond to potential exploitation attempts, particularly in environments where PRTG is used for critical monitoring operations. Regular security assessments of network monitoring tools should be conducted to identify similar vulnerabilities in other components of the security infrastructure.