CVE-2009-2299

Why Exploitable

The Artofdefence Hyperguard Web Application Firewall (WAF) module is vulnerable to a denial of service (DoS) attack due to its handling of HTTP requests with large Content-Length values but no POST data. This allows remote attackers to consume excessive memory, leading to a DoS condition.

• Empirical exploitation probability (EPSS) is not available for this CVE, which makes it difficult to assess the likelihood of exploitation.
• The absence of public exploit/PoC references and the CVE not being listed in CISA KEV reduces the urgency for immediate remediation.
• However, organizations should still validate their WAF module versions and update to the recommended versions (2.5.5-11635, 3.0.3-11636, or 3.1.1-11637) to prevent potential DoS attacks.

Overview

CVE-2009-2299 affects Artofdefence Hyperguard WAF modules for Apache HTTP Server across multiple 2.x/3.x lines before patched builds. Attackers allocate excessive memory by advertising huge Content-Length on empty POST requests.

Technical details

Faulty handling of Content-Length versus actual body bytes causes unbounded memory reservation in the WAF module path.

Impact

Denial of service via memory exhaustion on Apache workers protected by Hyperguard.

Exploitation steps

1. Find Hyperguard-protected Apache. 2. Send POST with large Content-Length, empty body. 3. Repeat to exhaust memory.

Indicators of compromise

Memory spikes; Hyperguard/Apache OOM; many identical POST patterns.

Mitigation and workarounds

Upgrade Hyperguard to fixed builds; rate-limit POSTs; cap Content-Length at proxy.

Community reactions

2009-era WAF advisory; emphasized validating declared lengths against delivered bytes.

Additional resources

• NVD CVE-2009-2299