CVE-2002-0871 in xinetd
Summary
by MITRE
xinetd 2.3.4 leaks file descriptors for the signal pipe to services that are launched by xinetd, which could allow those services to cause a denial of service via the pipe.
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Analysis
by VulDB Data Team • 06/27/2021
The vulnerability identified as CVE-2002-0871 represents a critical flaw in the xinetd superdaemon implementation that affects Unix-like operating systems. This issue manifests in the improper handling of file descriptors during service execution, specifically concerning signal pipe management within the xinetd framework. The vulnerability arises from the daemon's failure to correctly close or manage file descriptor references that are essential for signal handling between the parent xinetd process and its spawned child services. This design flaw creates a persistent resource leak that can be exploited by malicious actors or inadvertently triggered by service misbehavior.
The technical implementation of this vulnerability stems from the xinetd daemon's process management architecture where it creates signal pipes to communicate between parent and child processes. When xinetd launches services, it establishes these communication channels through file descriptors that should be properly closed after the service initialization phase. However, due to inadequate resource management within the xinetd codebase, these file descriptors remain open and accessible to the launched services. This creates a scenario where services can interact with the signal pipe through the leaked file descriptors, potentially causing the pipe to become corrupted or exhausted. The CWE-404 weakness classification applies here as the system fails to properly close or release file descriptor resources, leading to resource leakage that impacts system stability.
The operational impact of this vulnerability extends beyond simple resource consumption to potentially enable denial of service conditions that can severely impact system availability. When services launched by xinetd inherit these leaked file descriptors, they can inadvertently cause the signal pipe to malfunction, leading to communication breakdown between xinetd and its managed services. This can result in services becoming unresponsive or terminating unexpectedly, ultimately causing the xinetd daemon to fail in properly managing its service instances. The vulnerability is particularly concerning in environments where xinetd manages critical network services such as SSH, FTP, or other remote access protocols, as the denial of service can effectively disable network connectivity and system accessibility. According to ATT&CK framework, this vulnerability maps to T1499.004 (Endpoint Denial of Service) and T1566.001 (Phishing via Social Engineering), as it can be exploited to create service availability issues that may require system administrator intervention.
Mitigation strategies for CVE-2002-0871 should focus on immediate patch application and system hardening measures. The most effective solution involves updating to a patched version of xinetd that properly closes file descriptors after service initialization, preventing the inheritance of signal pipe references by spawned processes. System administrators should also implement monitoring for file descriptor usage patterns to detect potential leakage conditions before they escalate into denial of service scenarios. Additionally, implementing proper service isolation through containerization or virtualization techniques can limit the impact of such vulnerabilities by containing service processes within restricted environments. The vulnerability demonstrates the importance of proper resource management in daemon implementations and highlights the critical need for thorough testing of process management and file descriptor handling in system-level software components. Organizations should also consider migrating away from xinetd to more modern service management frameworks that provide better resource isolation and management capabilities.