CVE-2017-11507 in Check_MK
Summary
by MITRE
A cross site scripting (XSS) vulnerability exists in Check_MK versions 1.2.8x prior to 1.2.8p25 and 1.4.0x prior to 1.4.0p9, allowing an unauthenticated attacker to inject arbitrary HTML or JavaScript via the output_format parameter, and the username parameter of failed HTTP basic authentication attempts, which is returned unencoded in an internal server error page.
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Analysis
by VulDB Data Team • 12/13/2019
This cross site scripting vulnerability in Check_MK represents a critical security flaw that affects multiple versions of the popular network monitoring and system monitoring solution. The vulnerability stems from improper input validation and output encoding mechanisms within the application's handling of user-supplied data. Attackers can exploit this weakness by manipulating the output_format parameter and username parameter during failed HTTP basic authentication attempts to inject malicious HTML or JavaScript code. The vulnerability specifically manifests when the system returns unencoded user input in internal server error pages, creating an ideal environment for persistent cross site scripting attacks. This flaw exists in Check_MK versions prior to 1.2.8p25 and 1.4.0p9, indicating a significant window of exposure for organizations using affected versions of the monitoring platform.
The technical exploitation of this vulnerability follows established patterns of XSS attacks where user-controllable parameters are not properly sanitized before being rendered in web responses. The output_format parameter serves as the primary attack vector for unauthenticated attackers seeking to execute malicious scripts in the context of a victim's browser session. Additionally, the username parameter from failed authentication attempts provides a secondary exploitation pathway, as the system fails to encode this input before displaying it in error messages. This dual attack surface increases the likelihood of successful exploitation and demonstrates the systemic nature of the encoding deficiencies within the application's security architecture. The vulnerability aligns with CWE-79 which specifically addresses Cross-Site Scripting flaws and represents a classic example of improper output encoding in web applications.
The operational impact of this vulnerability extends beyond simple script execution, as it can enable attackers to perform session hijacking, steal sensitive monitoring data, and potentially escalate privileges within the monitoring environment. Organizations relying on Check_MK for critical infrastructure monitoring face significant risk from this vulnerability, as attackers could manipulate monitoring dashboards, inject malicious code into alert notifications, or redirect users to phishing sites. The unauthenticated nature of the attack means that even minimal network access can be leveraged to compromise the monitoring system, making it particularly dangerous in environments where Check_MK is exposed to untrusted networks or where authentication bypasses exist. This vulnerability directly impacts the integrity and confidentiality of monitoring data, potentially leading to undetected security incidents and compromised system visibility.
Organizations should immediately implement mitigations including upgrading to Check_MK versions 1.2.8p25 or 1.4.0p9, which contain the necessary patches for this vulnerability. Network segmentation and access controls should be enforced to limit exposure of the monitoring system to untrusted networks, while implementing proper input validation and output encoding mechanisms at the application level. Security monitoring should be enhanced to detect suspicious patterns in authentication attempts and unexpected HTML content in system responses. Additionally, organizations should conduct thorough vulnerability assessments of their monitoring infrastructure and implement web application firewalls to provide additional protection layers. This vulnerability demonstrates the critical importance of maintaining up-to-date security patches and proper input sanitization in monitoring and management systems, as these tools often serve as primary targets for attackers seeking persistent access to network infrastructure. The ATT&CK framework categorizes this as a web application attack vector with potential for privilege escalation and data exfiltration through the monitoring system's administrative interfaces.