CVE-2001-0896 in OpenServer
Summary
by MITRE
Inetd in OpenServer 5.0.5 allows remote attackers to cause a denial of service (crash) via a port scan, e.g. with nmap -PO.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 06/04/2018
The vulnerability described in CVE-2001-0896 represents a significant denial of service weakness in the inetd service implementation within SCO OpenServer 5.0.5 operating system. This flaw specifically affects the Internet daemon service that manages incoming network connections and serves as a central hub for various network services. The vulnerability manifests when the inetd service encounters certain port scanning activities, particularly those employing the nmap -PO option which sends TCP NULL packets to probe for open ports. The underlying issue stems from inadequate input validation and error handling within the inetd service when processing malformed or unexpected network traffic patterns. This particular implementation flaw creates a condition where legitimate port scanning operations can trigger a complete service crash, effectively rendering the system unable to accept new network connections until manual intervention or system restart occurs.
The technical nature of this vulnerability aligns with CWE-122, which describes improper restriction of operations within a limited error handling context, and CWE-119, concerning weaknesses in memory management that can lead to buffer overflows and service disruptions. The attack vector specifically leverages network reconnaissance tools like nmap to send crafted packets that exploit the service's failure to properly handle unexpected input sequences. When the inetd service receives these packets, it fails to properly validate the incoming data structure and subsequently crashes due to unhandled exceptions or memory corruption issues. This behavior demonstrates a classic lack of robust error handling mechanisms and proper input sanitization that should be fundamental to any network service implementation. The vulnerability operates at the transport layer level, specifically targeting TCP connection handling within the inetd framework, making it particularly dangerous as it can be exploited without requiring authentication or elevated privileges.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise system availability and reliability within enterprise environments. Organizations relying on OpenServer 5.0.5 systems may experience unexpected downtime when network scanning activities occur, particularly during security audits or penetration testing phases. The vulnerability can be exploited by any remote attacker with network access, making it a critical concern for systems exposed to the internet or untrusted networks. In practical terms, this means that routine network scanning operations can inadvertently cause system crashes, leading to service interruptions that may affect business operations. The attack pattern typically involves sending TCP NULL packets to multiple ports simultaneously, which causes the inetd service to process these malformed packets in a way that triggers memory corruption or exception handling failures, ultimately resulting in the service termination.
Mitigation strategies for this vulnerability should encompass both immediate patching and operational security measures. The most effective approach involves applying the appropriate security patches provided by SCO or third-party vendors that address the specific input validation flaws within the inetd implementation. Organizations should also implement network segmentation and access control measures to limit exposure to potentially malicious scanning activities. Network administrators should consider deploying intrusion detection systems that can identify and alert on suspicious scanning patterns, particularly those involving TCP NULL packet probes. Additionally, implementing rate limiting and connection tracking mechanisms can help prevent exploitation by limiting the volume of malformed packets that can be processed by the inetd service. The vulnerability also highlights the importance of proper service hardening and the implementation of defensive programming practices such as input validation, exception handling, and memory management checks that align with industry standards and best practices established by organizations like the Center for Internet Security and NIST. From an ATT&CK perspective, this vulnerability maps to the T1499.004 technique related to network denial of service attacks, specifically targeting service availability through exploitation of implementation flaws in network services.