Integer Underflow in P-Net Leading to DoS or Memory Disclosure

Executive Summary

P-Net before version 1.0.3 has an integer underflow vulnerability in the function pf_cpm_c_data_ind(). When processing a cyclic data frame while the consumer is in FRUN or RUN state, the offset for the APDU status is calculated as frame length minus 4 using 16-bit arithmetic without verifying sufficient frame length. A maliciously short frame causes the offset to wrap around, leading to out-of-bounds memory reads. This can crash the system or expose memory contents.

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Detection Guidance

Detecting this vulnerability requires monitoring for crashes or memory disclosure in systems running P-Net versions before 1.0.3. Check P-Net logs for segmentation faults or buffer overflow errors. Inspect network traffic for malformed cyclic data frames with lengths less than 4 bytes. Use tools like Wireshark to capture and analyze P-Net protocol traffic for unusually short frames.

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Impact Analysis

This vulnerability may cause denial of service by crashing the system or allow information disclosure by exposing memory contents. It requires network access to exploit and affects systems using P-Net versions before 1.0.3.

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Mitigation Strategies

Upgrade P-Net to version 1.0.3 or later immediately. If upgrading is not possible, restrict network access to P-Net devices to trusted sources only. Monitor system logs for signs of exploitation attempts. Implement input validation to reject frames shorter than the minimum required length.

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