CVE-2021-29643 in PRTG Network Monitor
Summary
by MITRE • 09/13/2021
PRTG Network Monitor before 21.3.69.1333 allows stored XSS via an unsanitized string imported from a User Object in a connected Active Directory instance.
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Analysis
by VulDB Data Team • 09/16/2021
The vulnerability identified as CVE-2021-29643 affects PRTG Network Monitor versions prior to 21.3.69.1333 and represents a critical stored cross-site scripting flaw that can be exploited through user object data imported from Active Directory instances. This vulnerability stems from inadequate input sanitization within the PRTG monitoring platform's handling of user attributes retrieved from integrated Active Directory environments. When PRTG imports user objects from Active Directory, it fails to properly sanitize string values that may contain malicious script content, creating a persistent XSS vector that can affect all users interacting with the compromised data.
The technical exploitation of this vulnerability occurs through the manipulation of user object attributes within Active Directory that are subsequently imported into PRTG's user management system. Attackers can inject malicious JavaScript code into user properties such as display names, descriptions, or other editable fields within Active Directory user objects. When these compromised user objects are imported into PRTG, the malicious content is stored within the system's database and executed whenever the affected user data is rendered in web interfaces. This stored nature of the vulnerability means that the malicious payload persists even after the initial injection, making it particularly dangerous for long-term exploitation and affecting multiple users over extended periods.
The operational impact of CVE-2021-29643 extends beyond simple script execution, as it can enable attackers to perform various malicious activities including credential theft, session hijacking, and data exfiltration. The vulnerability can be leveraged to steal authentication cookies or session tokens from authenticated users, potentially allowing attackers to impersonate legitimate users within the PRTG environment. Additionally, the stored XSS can be used to redirect users to malicious domains, install backdoors, or manipulate monitoring data to hide malicious activities from detection systems. Given that PRTG is widely used for network monitoring and management, the compromise of user data within this system can provide attackers with valuable insights into network infrastructure and potentially escalate to broader system compromises.
Organizations affected by this vulnerability should prioritize immediate remediation through the installation of PRTG Network Monitor version 21.3.69.1333 or later, which includes proper input sanitization for Active Directory user object attributes. The mitigation strategy should also include monitoring Active Directory user object modifications and implementing additional security controls such as web application firewalls that can detect and block malicious script patterns. Security teams should conduct thorough audits of imported user data and consider implementing privileged access management controls to limit the impact of potential exploitation. This vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and maps to ATT&CK technique T1078.004 for valid accounts and T1566.001 for spearphishing attachments, reflecting the attack vectors and exploitation methods that leverage such stored XSS vulnerabilities in enterprise monitoring systems.
The persistence of this vulnerability in PRTG's user management system demonstrates the critical importance of input validation in enterprise monitoring platforms that integrate with directory services. The vulnerability's impact is amplified in environments where PRTG serves as a central monitoring point for network infrastructure, as compromised user data can provide attackers with insights into network topology and potentially enable further attacks against other systems. Organizations should also consider implementing network segmentation and access controls to limit the potential damage from such vulnerabilities, ensuring that even if user data is compromised, the overall network infrastructure remains protected through proper security boundaries and monitoring controls.