CVE-2009-2299 in Hyperguard
Summary
by MITRE
The Artofdefence Hyperguard Web Application Firewall (WAF) module before 2.5.5-11635, 3.0 before 3.0.3-11636, and 3.1 before 3.1.1-11637, a module for the Apache HTTP Server, allows remote attackers to cause a denial of service (memory consumption) via an HTTP request with a large Content-Length value but no POST data.
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Analysis
by VulDB Data Team • 11/18/2018
The CVE-2009-2299 vulnerability affects the Artofdefence Hyperguard Web Application Firewall module, which serves as a security layer integrated with the Apache HTTP Server. This WAF module is designed to protect web applications from various cyber threats by filtering and monitoring HTTP requests. The vulnerability specifically impacts versions prior to 2.5.5-11635, 3.0.3-11636, and 3.1.1-11637, representing a critical flaw in how the module handles HTTP request processing. The issue manifests as a denial of service condition that can be triggered remotely, making it particularly dangerous for web applications that rely on this protection mechanism. This vulnerability falls under the category of resource exhaustion attacks, where an attacker can consume system resources to the point of rendering the service unavailable to legitimate users.
The technical flaw resides in the module's improper handling of HTTP requests containing large Content-Length headers without corresponding POST data. When the WAF processes such requests, it allocates memory based on the Content-Length value specified in the header, regardless of whether actual data is present in the request body. This memory allocation behavior creates a significant discrepancy between the expected and actual data processing, leading to excessive memory consumption. The vulnerability demonstrates a classic buffer over-allocation issue where the system reserves memory based on header information rather than actual data content. This flaw represents a weakness in input validation and resource management, aligning with CWE-129, which covers improper handling of length parameters. The attack vector involves sending a crafted HTTP request with an inflated Content-Length value, causing the WAF to allocate substantial memory resources that remain unused, ultimately leading to system resource exhaustion.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise the availability of web applications protected by the affected WAF module. When exploited, the vulnerability causes memory consumption to increase dramatically, potentially leading to system instability, application crashes, or complete service outages. Organizations relying on this WAF for protection face significant risk, as attackers can easily consume system resources without requiring authentication or advanced technical skills. The vulnerability affects the core functionality of the WAF, undermining its primary purpose of protecting web applications. From an attacker's perspective, this represents a low-effort, high-impact method of causing service disruption, making it particularly attractive for denial of service attacks. The vulnerability's remote nature means that attackers can exploit it from anywhere on the internet without requiring physical access to the system, amplifying its potential impact.
Mitigation strategies for CVE-2009-2299 primarily focus on updating the affected WAF module to versions that address the memory allocation flaw. Organizations should immediately upgrade to the patched versions mentioned in the advisory, specifically versions 2.5.5-11635, 3.0.3-11636, and 3.1.1-11637. Additionally, implementing rate limiting and request size restrictions at the network level can provide temporary protection while updates are being deployed. System administrators should monitor memory usage patterns and implement automated alerting for unusual resource consumption. Network administrators can also implement ingress filtering to limit the size of Content-Length headers that are accepted by the WAF. This vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a common pattern of resource exhaustion attacks that attackers use to disrupt services. Organizations should also consider implementing additional security monitoring to detect anomalous HTTP request patterns that might indicate exploitation attempts. The vulnerability highlights the importance of proper input validation and resource management in security modules, as improper handling of user-provided data can lead to critical system instability.