CVE-2007-6421 in HTTP Server
Summary
by MITRE
Cross-site scripting (XSS) vulnerability in balancer-manager in mod_proxy_balancer in the Apache HTTP Server 2.2.0 through 2.2.6 allows remote attackers to inject arbitrary web script or HTML via the (1) ss, (2) wr, or (3) rr parameters, or (4) the URL.
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Analysis
by VulDB Data Team • 08/03/2019
The vulnerability described in CVE-2007-6421 represents a critical cross-site scripting flaw within the Apache HTTP Server's mod_proxy_balancer module. This issue affects versions 2.2.0 through 2.2.6 and specifically targets the balancer-manager interface, which provides administrative functionality for managing load balancer configurations. The vulnerability stems from inadequate input validation and output encoding mechanisms within the server's response handling for proxy balancer management parameters. Attackers can exploit this weakness by manipulating specific URL parameters to inject malicious scripts that execute in the context of authenticated users' browsers, potentially leading to complete session hijacking or unauthorized administrative actions.
The technical exploitation occurs through four distinct parameter vectors: ss, wr, rr, and the URL itself. These parameters control various aspects of the load balancer's operational state and configuration management within the balancer-manager interface. When these parameters are processed without proper sanitization, they become entry points for malicious input that gets directly rendered in the web page output. The vulnerability specifically maps to CWE-79, which defines Cross-Site Scripting as a weakness where untrusted data is used to generate web content without proper validation or encoding, allowing attackers to inject hostile scripts into web applications. The flaw represents a classic case of improper neutralization of input during web page generation, making it particularly dangerous in administrative contexts where users have elevated privileges.
The operational impact of this vulnerability extends beyond simple script injection, as it enables attackers to manipulate the load balancer's configuration and potentially compromise the entire web infrastructure. An attacker who successfully exploits this vulnerability could modify load balancer settings, redirect traffic to malicious endpoints, or gain unauthorized access to administrative functions. The risk is amplified because the balancer-manager interface typically requires authentication, making the attack vector particularly insidious as it can be leveraged to escalate privileges or perform unauthorized administrative actions. This vulnerability directly aligns with ATT&CK technique T1059.007, which covers Scripting through the execution of malicious scripts in web contexts, and T1566.002, which involves social engineering via web-based phishing attacks that could exploit this XSS weakness.
Mitigation strategies for CVE-2007-6421 require immediate patching of affected Apache HTTP Server installations to versions 2.2.7 or later, where the XSS vulnerability has been addressed through proper input validation and output encoding. Organizations should implement comprehensive input sanitization measures that validate and filter all user-supplied parameters before processing them within the web application context. Network administrators should also consider implementing additional security controls such as web application firewalls that can detect and block malicious script injection attempts. The remediation process must include thorough testing of the patched environment to ensure that legitimate functionality remains intact while eliminating the XSS attack vectors. Security teams should conduct regular vulnerability assessments to identify similar weaknesses in other web applications and ensure proper security hardening practices are implemented across all server components.