CVE-2011-2904 in Zabbix
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in acknow.php in Zabbix before 1.8.6 allows remote attackers to inject arbitrary web script or HTML via the backurl parameter.
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Analysis
by VulDB Data Team • 11/18/2021
The CVE-2011-2904 vulnerability represents a classic cross-site scripting flaw in the Zabbix monitoring platform, specifically within the acknow.php script. This vulnerability exists in Zabbix versions prior to 1.8.6 and allows remote attackers to execute malicious web scripts or HTML code through manipulation of the backurl parameter. The issue stems from insufficient input validation and output sanitization mechanisms within the acknowledgment processing functionality of the monitoring system. When a user navigates to the acknow.php page and provides a crafted backurl parameter, the application fails to properly escape or filter the input before incorporating it into the HTTP response, creating an avenue for malicious code execution.
The technical implementation of this vulnerability aligns with CWE-79, which defines Cross-Site Scripting as a weakness where untrusted data is incorporated into web pages without proper validation or sanitization. In the context of Zabbix, the backurl parameter serves as the injection vector where attackers can embed malicious payloads that will execute in the context of other users' browsers who visit the affected page. This particular implementation allows for arbitrary code execution within the victim's browser session, potentially enabling session hijacking, credential theft, or redirection to malicious sites. The vulnerability operates at the application layer and requires no special privileges to exploit, making it particularly dangerous in environments where Zabbix is used for critical infrastructure monitoring.
The operational impact of CVE-2011-2904 extends beyond simple script injection, as it can compromise the integrity of the entire monitoring infrastructure. Attackers who successfully exploit this vulnerability can manipulate the acknowledgment process, potentially causing false alerts or redirecting users to malicious sites while they are authenticated to the Zabbix system. This creates a significant risk for organizations relying on Zabbix for system monitoring, as compromised monitoring interfaces can provide attackers with insights into network operations and potentially facilitate further attacks. The vulnerability also violates the principle of least privilege, as a single malicious input can affect all users of the monitoring platform, undermining the security posture of the entire infrastructure.
Mitigation strategies for CVE-2011-2904 primarily involve immediate patching of affected Zabbix installations to version 1.8.6 or later, where the vulnerability has been addressed through proper input validation and output sanitization. Organizations should also implement comprehensive web application firewall rules to detect and block malicious backurl parameter values, particularly those containing common XSS payload patterns such as script tags, event handlers, or encoded javascript. Additionally, security teams should conduct regular input validation audits of web applications, ensuring that all user-supplied data is properly escaped before being rendered in web responses. The ATT&CK framework categorizes this vulnerability under T1059.007 for scripting and T1566 for phishing, highlighting the need for both technical controls and user awareness training to prevent exploitation. Network segmentation and access controls should be implemented to limit the potential impact of successful exploitation, while regular security assessments should verify that similar vulnerabilities do not exist in other components of the monitoring infrastructure.