CVE-2003-0464 in Linux
Summary
by MITRE
The RPC code in Linux kernel 2.4 sets the reuse flag when sockets are created, which could allow local users to bind to UDP ports that are used by privileged services such as nfsd.
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Analysis
by VulDB Data Team • 05/04/2019
The vulnerability described in CVE-2003-0464 represents a critical socket implementation flaw within the Linux kernel version 2.4 that affects the remote procedure call subsystem. This issue stems from the improper handling of socket reuse flags during the creation of network sockets, specifically impacting UDP port binding operations. The fundamental problem lies in how the kernel manages socket lifecycle and port allocation, creating an unexpected pathway for privilege escalation through unauthorized port binding.
The technical implementation flaw occurs when the kernel's RPC code sets the SO_REUSEADDR flag on sockets during creation, allowing non-privileged users to bind to ports that are typically restricted to privileged processes. This behavior violates standard socket security conventions and creates a direct attack vector for local users to impersonate privileged services. The vulnerability specifically impacts the Network File System daemon nfsd which relies on specific UDP ports for its operation, making it susceptible to port hijacking by unauthorized local users.
From an operational perspective, this vulnerability enables local users to potentially gain elevated privileges by binding to UDP ports used by privileged services, effectively allowing them to intercept or manipulate network traffic intended for legitimate privileged processes. The attack surface extends beyond just nfsd to any service that depends on specific UDP port bindings, creating a widespread security risk across network services. This issue directly relates to CWE-264, which addresses permissions, privileges, and access controls in software implementations, and aligns with ATT&CK technique T1068, which covers local privilege escalation through system configuration vulnerabilities.
The security implications of this vulnerability are significant as it allows attackers to perform man-in-the-middle attacks or service disruption by binding to critical ports used by privileged services. Network administrators and security professionals must understand that this vulnerability represents a fundamental breakdown in kernel-level socket security mechanisms. The exploitation requires local system access but provides substantial privilege escalation capabilities, making it particularly dangerous in multi-user environments where local access is commonly available.
Mitigation strategies for this vulnerability involve kernel-level patches that correct the socket reuse flag behavior and ensure proper port binding restrictions. System administrators should implement immediate kernel updates to address this issue, as the vulnerability cannot be effectively mitigated through network-level configurations or firewall rules. The recommended approach includes applying the appropriate kernel security patches and implementing proper access controls to limit local user privileges. Additionally, monitoring for unauthorized socket binding operations and implementing network segmentation can help reduce the attack surface, though these measures do not address the root cause of the vulnerability within the kernel's RPC implementation.