CVE-2001-1395 in Linux
Summary
by MITRE
Unknown vulnerability in sockfilter for Linux kernel before 2.2.19 related to "boundary cases," with unknown impact.
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Analysis
by VulDB Data Team • 06/25/2021
The vulnerability identified as CVE-2001-1395 represents a critical security flaw within the Linux kernel's sockfilter implementation affecting systems running kernel versions prior to 2.2.19. This issue specifically targets the socket filtering mechanism that operates at the kernel level to control network packet filtering and processing. The sockfilter functionality serves as a crucial component in the kernel's networking stack, enabling the implementation of sophisticated packet filtering rules through the BPF (Berkeley Packet Filter) mechanism that allows userspace applications to specify filtering criteria for network traffic. The vulnerability's classification as "unknown impact" suggests that the exact nature of the security breach was not fully understood at the time of reporting, though it was recognized as potentially severe given its location within core kernel networking functionality.
The technical flaw manifests in what the vulnerability description terms as "boundary cases" within the sockfilter implementation, indicating that the issue occurs under specific edge conditions that are not properly handled during packet processing. Boundary case vulnerabilities typically arise when software fails to adequately validate or process inputs at their extreme limits or when state transitions occur in unexpected ways. In kernel space, such failures can lead to privilege escalation, denial of service conditions, or potentially arbitrary code execution depending on the nature of the boundary condition. The sockfilter subsystem processes network packets through a series of filtering rules that are compiled into BPF bytecode, and the boundary case scenario likely involves malformed packet data or edge-case filtering rules that cause the kernel to behave unpredictably during the packet processing loop.
The operational impact of this vulnerability extends beyond simple network functionality degradation, as kernel-level flaws in networking components can compromise entire system security posture. Systems utilizing affected kernel versions may experience unexpected crashes, system instability, or potential privilege escalation attacks that could allow malicious actors to gain unauthorized access to system resources. The sockfilter mechanism is commonly used by network monitoring tools, intrusion detection systems, and various security applications that rely on kernel-level packet filtering for their operations. When compromised, these systems become vulnerable to exploitation that could result in complete system compromise, data exfiltration, or the establishment of persistent backdoors. The vulnerability's presence in kernel versions before 2.2.19 indicates that it was likely present for an extended period, potentially allowing attackers to develop and deploy exploits against systems that had not yet been patched.
Mitigation strategies for this vulnerability center primarily on kernel version updates to 2.2.19 or later, which would incorporate the necessary patches to address the boundary case handling in the sockfilter implementation. System administrators should prioritize immediate patching of affected systems, particularly those running older kernel versions that may be exposed to network-based attacks. The vulnerability's nature as a kernel-level boundary case issue aligns with CWE-129, which describes improper validation of array indices, and may also relate to CWE-128, concerning wrapping or truncation of integer values. From an ATT&CK perspective, this vulnerability could be leveraged as part of initial access or privilege escalation tactics, potentially enabling adversaries to establish persistence through kernel-level modifications or to conduct reconnaissance activities that exploit the unstable packet filtering behavior. Organizations should implement comprehensive monitoring for system instability or unexpected network behavior that could indicate exploitation attempts, while also ensuring that all network security tools relying on sockfilter functionality are updated to compatible kernel versions before deployment on production systems.