BPF Division by Zero in libpcap

Executive Summary

This vulnerability is a division by zero issue in the libpcap library's BPF interpreter. It occurs when handling 'div #k' and 'mod #k' ALU instructions where the immediate value 'k' is zero. The interpreter fails to validate this case, leading to a crash when processing crafted filter programs.

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Detection Guidance

To detect this vulnerability, monitor for crashes or SIGFPE signals in applications using libpcap, particularly those processing BPF filter programs. Check logs for division by zero errors in libpcap-related processes. Use tools like strace or gdb to trace execution when processing crafted BPF filters.

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Impact Analysis

If exploited, this vulnerability could cause a denial of service by crashing the process handling the malicious BPF filter. This affects applications using libpcap for packet capture or filtering, potentially disrupting network monitoring or security tools.

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Mitigation Strategies

Update libpcap to the latest patched version. Avoid using externally generated BPF filter programs or validate them before use. Restrict access to applications that use libpcap to trusted users only. Monitor for unusual crashes in network monitoring tools.

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