Detection Guidance

This vulnerability can be detected by monitoring for crashes or abnormal behavior in services or vessel systems that process AIS data using libais, especially when receiving AIS sentences with empty or out-of-range sequential message IDs.

Since the vulnerability is triggered by specially crafted AIVDM sentences sent over VHF marine radio or IP feeds, inspecting incoming AIS messages for invalid or empty sequence ID fields can help detect attempts to exploit this issue.

Specific commands are not provided in the resources, but network or system administrators can use packet capture tools (e.g., tcpdump or Wireshark) to filter and analyze AIS traffic for malformed AIVDM sentences with suspicious sequence ID values.

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Mitigation Strategies

Immediate mitigation involves updating libais to a version where runtime bounds checking is implemented before indexing the vector, as the vulnerability is caused by unchecked use of sequence IDs.

Until a patched version is applied, monitoring and filtering incoming AIS messages to block or drop those with empty or out-of-range sequential message IDs can reduce the risk of exploitation.

Additionally, applying network-level controls to restrict or validate AIS data sources, and employing intrusion detection systems to alert on malformed AIS sentences, can help mitigate potential attacks.

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Executive Summary

This vulnerability exists in libais through version 0.15, specifically in the VdmStream::AddLine function. The issue arises because the function uses an unchecked sentinel value as a vector index when processing AIS sentences that have empty or out-of-range sequential message IDs.

As a result, remote attackers can exploit this by sending specially crafted AIVDM sentences over VHF marine radio or IP feeds. This causes out-of-bounds memory access, which can lead to crashes or potential memory corruption in services or vessel systems that use this library.

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Impact Analysis

The vulnerability can impact you by allowing remote attackers to crash services or vessel systems that rely on the libais library for processing AIS data. This can disrupt normal operations by causing out-of-bounds memory access and potential memory corruption.

Such crashes could lead to denial of service conditions, potentially affecting the safety and reliability of marine navigation or communication systems.

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