CVE-2009-4441 in Java System Directory Server
Summary
by MITRE
Directory Proxy Server (DPS) in Sun Java System Directory Server Enterprise Edition 6.0 through 6.3.1 does not enable the SO_KEEPALIVE socket option, which makes it easier for remote attackers to cause a denial of service (connection slot exhaustion) via multiple connections, aka Bug Id 6782659.
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Analysis
by VulDB Data Team • 08/30/2021
The vulnerability identified as CVE-2009-4441 affects the Sun Java System Directory Server Enterprise Edition version 6.0 through 6.3.1, specifically within the Directory Proxy Server component. This issue represents a significant security weakness that impacts the server's ability to manage network connections effectively. The flaw lies in the server's failure to properly configure the SO_KEEPALIVE socket option, which is a fundamental TCP networking parameter that enables periodic keepalive probes to detect dead connections. The vulnerability exposes the system to potential denial of service attacks by allowing remote attackers to consume available connection slots without proper cleanup mechanisms.
The technical implementation of this vulnerability stems from the Directory Proxy Server's network socket configuration where the SO_KEEPALIVE option remains disabled. This configuration prevents the server from automatically detecting and closing inactive or broken network connections, leading to connection slot exhaustion. When attackers establish multiple connections to the server without properly closing them, these connections remain in a lingering state consuming system resources. The absence of keepalive probes means the server cannot distinguish between active connections and dead ones, resulting in a gradual depletion of available connection slots. According to the CWE catalog, this represents a weakness in the system's resource management and connection handling mechanisms, specifically categorized under CWE-1001 as a weakness in the design of the system's network communication layer. The vulnerability's impact is amplified by the fact that it operates at the network protocol level, making it particularly effective against systems that do not implement proper connection lifecycle management.
The operational impact of CVE-2009-4441 creates a substantial risk for directory server deployments where the server may become unresponsive or completely unavailable due to connection slot exhaustion. Attackers can exploit this vulnerability by maintaining numerous persistent connections to the server, gradually consuming all available connection slots and preventing legitimate users from establishing new connections. This type of attack aligns with the MITRE ATT&CK framework's tactic of privilege escalation through resource exhaustion, specifically targeting the server's availability. The vulnerability affects the server's availability and performance, potentially causing cascading failures in directory-dependent applications and services. Organizations relying on the Directory Server Enterprise Edition may experience service disruption, authentication failures, and degraded performance that can impact critical business operations. The vulnerability's exploitation requires minimal technical expertise, making it particularly dangerous as it can be leveraged by attackers with basic network knowledge.
Mitigation strategies for CVE-2009-4441 primarily involve implementing proper system configuration changes to enable the SO_KEEPALIVE socket option on the Directory Proxy Server. Administrators should configure the server to automatically detect and close inactive connections through proper socket option settings, typically involving the TCP keepalive parameters. The most effective immediate solution involves applying the vendor's security patches or updates that address this specific socket configuration issue. System administrators should also implement connection limiting mechanisms and monitoring to detect unusual connection patterns that may indicate exploitation attempts. Network-level mitigations include implementing connection rate limiting at the firewall or load balancer level to prevent abuse of the vulnerable server. Additionally, organizations should establish regular monitoring of connection states and implement automated alerting for unusual connection patterns. The implementation of proper connection lifecycle management and resource cleanup procedures will help prevent the accumulation of stale connections that contribute to the vulnerability's exploitation. Security hardening practices should include regular vulnerability assessments to identify similar socket configuration issues across the organization's network infrastructure.