CVE-2016-9798 in BlueZ
Summary
by MITRE
In BlueZ 5.42, a use-after-free was identified in "conf_opt" function in "tools/parser/l2cap.c" source file. This issue can be triggered by processing a corrupted dump file and will result in hcidump crash.
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Analysis
by VulDB Data Team • 06/15/2019
The vulnerability identified as CVE-2016-9798 represents a critical use-after-free flaw within the BlueZ Bluetooth protocol stack version 5.42. This issue resides in the configuration option parsing functionality of the hcidump tool, specifically within the "conf_opt" function located in "tools/parser/l2cap.c". The BlueZ stack serves as the primary Bluetooth protocol implementation for Linux systems, making this vulnerability particularly concerning for widespread exploitation. The flaw manifests when the system processes malformed or corrupted dump files that contain improperly structured Bluetooth protocol data, creating a scenario where memory previously freed by the application is accessed again, leading to unpredictable behavior and potential system instability.
The technical execution of this vulnerability involves the improper handling of memory allocation and deallocation within the parser component of hcidump. When a corrupted dump file is processed, the parser attempts to parse configuration options from the malformed data structure, leading to a situation where the "conf_opt" function operates on memory that has already been freed. This memory corruption occurs during the parsing of L2CAP (Logical Link Control and Adaptation Protocol) packet data, which forms a fundamental part of Bluetooth communication layers. The use-after-free condition creates a scenario where the application may attempt to read or write to memory locations that have been deallocated, potentially allowing an attacker to manipulate the program flow or cause a denial of service condition.
The operational impact of CVE-2016-9798 extends beyond simple application crashes to potentially enable more sophisticated attack vectors. While the immediate effect is a hcidump crash that disrupts Bluetooth protocol analysis activities, the underlying memory corruption could theoretically be exploited to achieve arbitrary code execution or privilege escalation within the context of the affected system. This vulnerability particularly affects systems running BlueZ 5.42 and earlier versions where Bluetooth protocol analysis tools are utilized, including embedded systems, servers, and desktop environments that rely on Bluetooth functionality. The issue is classified under CWE-416, which specifically addresses the use of freed memory, and aligns with ATT&CK technique T1059 for command and scripting interpreter usage in exploitation scenarios.
Mitigation strategies for this vulnerability require immediate patching of affected BlueZ installations to version 5.44 or later, where the memory management issues have been addressed through proper bounds checking and memory deallocation practices. System administrators should also implement strict file validation procedures for any Bluetooth dump files processed by hcidump, particularly in environments where untrusted data sources are present. Additional protective measures include running hcidump with reduced privileges, implementing network segmentation for Bluetooth traffic, and employing intrusion detection systems to monitor for suspicious Bluetooth protocol analysis activities. Organizations should also consider disabling unnecessary Bluetooth protocol analysis tools when they are not actively needed, as this reduces the attack surface for potential exploitation of the use-after-free vulnerability. The vulnerability demonstrates the importance of proper memory management in network protocol parsing components and highlights the need for rigorous input validation in security-critical system tools.