Bluetooth RFCOMM Memory Corruption in Linux Kernel

Mitigation Strategies

The vulnerability is resolved by validating the skb length in RFCOMM MCC handlers in the Linux kernel. Immediate mitigation steps include updating the Linux kernel to a version where this fix is applied.

Specifically, the fix involves using skb_pull_data() to validate and access the required data before dereferencing it, preventing out-of-bounds reads caused by truncated MCC frames.

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Executive Summary

This vulnerability exists in the Linux kernel's Bluetooth RFCOMM MCC handlers. These handlers cast the skb->data pointer to protocol-specific structures without first validating the length of the skb (socket buffer). A malicious remote device can exploit this by sending truncated MCC frames, which causes the handlers to perform out-of-bounds reads of memory.

The issue is fixed by using skb_pull_data() to validate and safely access the required data before dereferencing it. Special handling is applied to the rfcomm_recv_rpn() function because the protocol allows 1-byte RPN requests, so it validates the DLCI byte first and the full structure only if the length is greater than one.

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Impact Analysis

This vulnerability can allow a malicious remote Bluetooth device to cause out-of-bounds memory reads in the Linux kernel's Bluetooth RFCOMM MCC handlers. Such out-of-bounds reads can potentially lead to information disclosure, system instability, or crashes, depending on how the kernel handles the invalid memory access.

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