CVE-2016-9802 in BlueZ
Summary
by MITRE
In BlueZ 5.42, a buffer over-read was identified in "l2cap_packet" function in "monitor/packet.c" source file. This issue can be triggered by processing a corrupted dump file and will result in btmon crash.
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Analysis
by VulDB Data Team • 06/15/2019
The vulnerability identified in CVE-2016-9802 represents a critical buffer over-read condition within the BlueZ Bluetooth protocol stack version 5.42. This flaw exists in the l2cap_packet function located in the monitor/packet.c source file, which serves as a crucial component for monitoring and analyzing Bluetooth Low Energy and classic Bluetooth traffic. The issue manifests when the btmon utility processes corrupted or malformed dump files, creating a scenario where the application attempts to read memory beyond the allocated buffer boundaries. Such buffer over-read conditions typically arise from inadequate input validation and boundary checking mechanisms within the packet parsing logic, allowing attackers to potentially exploit memory access violations that could lead to application instability or more severe consequences.
The technical exploitation of this vulnerability occurs through the manipulation of dump files that contain malformed L2CAP (Logical Link Control and Adaptation Protocol) packets. When btmon attempts to parse these corrupted files, the l2cap_packet function fails to properly validate the length and structure of incoming data, causing it to access memory locations that have not been allocated for the current packet processing operation. This specific flaw falls under the CWE-125 vulnerability category, which defines out-of-bounds read conditions where programs access memory beyond the intended buffer limits. The buffer over-read in this context represents a classic example of improper input validation where the application assumes all input data conforms to expected formats without sufficient sanitization checks.
The operational impact of CVE-2016-9802 extends beyond simple application crashes, as it demonstrates a fundamental weakness in the Bluetooth monitoring infrastructure that could be leveraged by adversaries. When btmon crashes due to this buffer over-read, it not only interrupts the monitoring capabilities of Bluetooth traffic analysis but also potentially exposes the underlying system to further instability. In environments where continuous Bluetooth monitoring is critical for security operations or network analysis, such a vulnerability could provide attackers with a reliable method for disrupting legitimate monitoring activities. The vulnerability aligns with ATT&CK technique T1059.001, which involves the use of command-line interfaces and system utilities, as the btmon utility represents a legitimate system tool that could be targeted to cause denial of service or system instability.
Mitigation strategies for this vulnerability require immediate patching of BlueZ installations to versions that address the buffer over-read condition in the l2cap_packet function. System administrators should ensure that all instances of btmon are updated to patched versions of BlueZ, as the vulnerability specifically affects the monitoring component rather than core Bluetooth functionality. Additionally, organizations should implement strict input validation for any dump files processed by btmon, including verification of file integrity and format compliance before analysis. Network security teams should also consider implementing monitoring for abnormal btmon behavior or crashes, as these incidents could indicate attempted exploitation of the vulnerability. The fix typically involves adding proper boundary checks and input validation within the packet parsing logic to prevent access beyond allocated buffer limits, which aligns with security best practices for preventing memory corruption vulnerabilities.