CVE-2001-1393 in Linux
Summary
by MITRE
Unknown vulnerability in classifier code for Linux kernel before 2.2.19 could result in denial of service (hang).
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Analysis
by VulDB Data Team • 07/19/2019
The vulnerability identified as CVE-2001-1393 represents a critical flaw within the Linux kernel's classifier code that existed prior to version 2.2.19. This issue manifests as a denial of service condition that can cause system hang, effectively rendering the affected system non-responsive and unable to process further requests. The classifier code in question is responsible for network packet classification and filtering operations, which form a fundamental component of the kernel's networking stack. When exploited, this vulnerability can bring entire network operations to a complete halt, making it particularly dangerous in production environments where network availability is paramount.
The technical nature of this flaw lies within the kernel's packet classification mechanisms, which are typically implemented as part of the netfilter framework or similar packet filtering subsystems. The vulnerability likely stems from improper handling of packet data structures or insufficient input validation within the classifier functions. This type of issue commonly falls under CWE-129 Input Validation, where inadequate bounds checking or improper state management leads to system instability. The vulnerability may be triggered through malformed network packets or specific packet sequences that cause the classifier code to enter an unrecoverable state, potentially leading to infinite loops or deadlock conditions within kernel memory management routines.
The operational impact of CVE-2001-1393 extends beyond simple service disruption to encompass potential system compromise and availability attacks. An attacker capable of sending malicious network traffic could exploit this vulnerability to perform denial of service attacks against targeted systems, potentially affecting network services, applications, and overall system responsiveness. The hanging condition could persist until system reboot, making it particularly damaging in mission-critical environments. This vulnerability aligns with ATT&CK technique T1499.004 Network Denial of Service, where adversaries leverage system weaknesses to disrupt network communications and availability. The impact is exacerbated in environments where network classification is heavily utilized, such as firewalls, routers, and network monitoring systems that rely on kernel-level packet filtering.
Mitigation strategies for this vulnerability require immediate kernel updates to versions 2.2.19 or later where the flaw has been addressed through proper input validation and state management within the classifier code. System administrators should prioritize patching affected systems, particularly those operating in network-intensive environments. Network administrators may also implement additional monitoring to detect unusual packet patterns that could indicate exploitation attempts, though this represents a reactive measure rather than a permanent fix. The vulnerability demonstrates the critical importance of kernel security updates and proper input validation in operating system components, as even seemingly minor flaws in core networking code can result in complete system compromise through denial of service attacks. Organizations should maintain robust patch management processes and conduct regular security assessments to identify and remediate similar vulnerabilities in their kernel implementations.