CVE-2003-0643 in Linux
Summary
by MITRE
Integer signedness error in the Linux Socket Filter implementation (filter.c) in Linux 2.4.3-pre3 to 2.4.22-pre10 allows attackers to cause a denial of service (crash).
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Analysis
by VulDB Data Team • 06/28/2021
The vulnerability identified as CVE-2003-0643 represents a critical integer signedness error within the Linux kernel's socket filter implementation, specifically in the filter.c file. This flaw exists in Linux kernel versions ranging from 2.4.3-pre3 through 2.4.22-pre10, affecting systems that utilize the Berkeley Packet Filter (BPF) subsystem for network packet filtering and monitoring. The issue stems from improper handling of signed and unsigned integer operations during the processing of socket filter instructions, creating a condition where malicious input can trigger unexpected behavior in the kernel's memory management and execution flow.
The technical implementation of this vulnerability occurs when the kernel processes BPF instructions that involve integer operations, particularly in the context of packet filtering rules. When an attacker crafts malicious BPF programs with specific instruction sequences that exploit the signedness mismatch, the kernel's filter processing logic fails to properly validate or handle the integer values, leading to buffer overflows or invalid memory access patterns. This signedness error manifests during the interpretation of filter programs, where the kernel's assumption about integer value ranges becomes incorrect, causing the execution path to diverge into unexpected code sections that ultimately result in system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it represents a fundamental weakness in the kernel's security model that could potentially be exploited for more sophisticated attacks. Systems utilizing BPF for network monitoring, intrusion detection, or packet filtering are particularly at risk, as attackers can craft malicious filter programs that cause kernel crashes, system reboots, or even potential privilege escalation in certain configurations. The vulnerability affects the core networking functionality of affected systems, making it particularly dangerous in server environments where network traffic processing is critical for system operation.
Mitigation strategies for CVE-2003-0643 primarily involve upgrading to patched kernel versions, specifically Linux 2.4.22 or later where the signedness error has been corrected through proper integer type handling and validation routines. System administrators should also implement network segmentation and access controls to limit who can submit BPF programs to affected systems, as the vulnerability requires the ability to load or execute malicious filter code. Additionally, monitoring for unusual network traffic patterns or system crashes that might indicate exploitation attempts can provide early warning of potential attacks. The vulnerability aligns with CWE-190, which describes integer overflow and underflow conditions, and falls within ATT&CK technique T1059 for execution through kernel modules or system calls. Organizations should also consider implementing kernel hardening measures such as stack canaries, address space layout randomization, and kernel module signing to reduce the overall attack surface and potential impact of such vulnerabilities in their network infrastructure.