CVE-2019-9206 in PRTG Network Monitor
Summary
by MITRE
PRTG Network Monitor v7.1.3.3378 allows XSS via the /public/login.htm errormsg or loginurl parameter. NOTE: This product is discontinued.
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Analysis
by VulDB Data Team • 05/17/2020
PRTG Network Monitor version 7.1.3.3378 contains a cross-site scripting vulnerability that affects the public login page through the errormsg or loginurl parameters. This vulnerability represents a classic input validation flaw where user-supplied data is not properly sanitized before being rendered in the web interface. The issue occurs when the application processes these parameters without implementing adequate output encoding or validation mechanisms, allowing malicious actors to inject malicious scripts that execute in the context of other users' browsers.
The technical flaw stems from insufficient parameter validation within the authentication flow of the discontinued PRTG Network Monitor application. When the system processes the errormsg or loginurl parameters, it fails to sanitize user input before displaying it on the login page. This creates an environment where an attacker can craft malicious payloads that, when processed by the vulnerable application, execute in the browser context of authenticated users. The vulnerability aligns with CWE-79 which specifically addresses cross-site scripting flaws due to improper input handling and output encoding. This weakness enables attackers to potentially steal session cookies, perform unauthorized actions on behalf of users, or redirect victims to malicious sites.
The operational impact of this vulnerability is significant given that PRTG Network Monitor is a widely used network monitoring solution that typically requires administrative privileges and handles sensitive network data. An attacker exploiting this XSS vulnerability could gain access to authenticated sessions, potentially leading to full system compromise or unauthorized network monitoring activities. The vulnerability affects the authentication mechanism itself, making it particularly dangerous as it could be leveraged to escalate privileges or redirect users to phishing sites. This represents a critical security risk in enterprise environments where network monitoring tools often serve as central points of access to sensitive infrastructure information.
Organizations should immediately implement mitigations including disabling the affected version of PRTG Network Monitor and migrating to supported versions that address this vulnerability. Input validation should be strengthened through proper parameter sanitization and output encoding practices. The application should implement Content Security Policy headers to prevent unauthorized script execution. Additionally, security teams should monitor for any exploitation attempts and consider network segmentation to limit the attack surface. Given that this product is discontinued, organizations should plan migration to supported network monitoring solutions that maintain current security standards and receive regular updates. This vulnerability demonstrates the importance of maintaining up-to-date security practices and the risks associated with using unsupported software in production environments. The ATT&CK framework categorizes this as a web application vulnerability that could enable initial access or privilege escalation through social engineering or session hijacking techniques.