Integer Overflow in SpaceDot AcubeSAT OBC Software

Executive Summary

This vulnerability is an integer handling flaw in the cobs_decode function of SpaceDot AcubeSAT OBC software. It involves two issues: signed vs. unsigned comparison and 8-bit truncation. The first issue causes a negative pointer difference to be treated as a large unsigned value, bypassing buffer checks. The second issue discards upper bits when calculating buffer space, potentially leading to out-of-bounds memory access.

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Detection Guidance

Detecting this vulnerability requires checking for integer handling flaws in the cobs_decode function of the AcubeSAT OBC software. Monitor for out-of-bounds reads or buffer overflows during COBS-encoded data processing via USART serial interface. Inspect memory access patterns for negative pointer differences or 8-bit truncation issues in buffer boundary checks.

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Impact Analysis

An attacker with physical access to the USART serial interface could exploit this flaw to cause a Denial of Service (DoS) by sending crafted input. While the current 128-byte buffer limits exploitability, malformed COBS data might trigger error conditions. The system continues processing messages, preventing full system-wide DoS.

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Mitigation Strategies

Immediately restrict physical access to the USART serial interface to prevent unauthorized UART access. Update the cobs_decode function to use consistent unsigned integer types for buffer boundary checks. Validate input data to ensure it does not trigger negative pointer differences or 8-bit truncation issues.

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