CVE-2021-41229 in BlueZ
Summary
by MITRE • 11/13/2021
BlueZ is a Bluetooth protocol stack for Linux. In affected versions a vulnerability exists in sdp_cstate_alloc_buf which allocates memory which will always be hung in the singly linked list of cstates and will not be freed. This will cause a memory leak over time. The data can be a very large object, which can be caused by an attacker continuously sending sdp packets and this may cause the service of the target device to crash.
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Analysis
by VulDB Data Team • 11/04/2025
The vulnerability identified as CVE-2021-41229 resides within the BlueZ Bluetooth protocol stack implementation for Linux systems, representing a critical memory management flaw that can lead to resource exhaustion and service disruption. This issue affects the sdp_cstate_alloc_buf function which handles allocation of memory buffers during Bluetooth service discovery protocol operations, creating a persistent memory leak condition that accumulates over time. The vulnerability specifically targets the control state management mechanism within BlueZ, where allocated memory blocks become permanently stranded in singly linked lists of control states, preventing proper garbage collection and memory reuse.
The technical flaw manifests through improper memory deallocation practices within the Bluetooth service discovery protocol handler, where the sdp_cstate_alloc_buf function allocates memory buffers that remain referenced in linked list structures even after their intended use has concluded. This creates a memory leak scenario where each processed sdp packet can trigger additional memory allocations that are never properly freed, leading to progressive memory consumption. The vulnerability is particularly dangerous because attackers can exploit this by continuously transmitting specially crafted sdp packets to the target device, causing the memory leak to accelerate and eventually result in system resource exhaustion.
The operational impact of CVE-2021-41229 extends beyond simple memory consumption, as the persistent memory leak can lead to complete service unavailability and system instability. When the target device's memory becomes saturated due to the accumulation of unreleased control state buffers, the Bluetooth service may crash or become unresponsive, effectively denying legitimate users access to Bluetooth functionality. This vulnerability particularly affects embedded systems, IoT devices, and mobile platforms that rely on BlueZ for Bluetooth operations, where memory resources are often constrained and the impact of resource exhaustion is magnified. The attack surface is broad as any device running affected versions of BlueZ that processes incoming sdp packets is potentially vulnerable.
Mitigation strategies for CVE-2021-41229 should focus on immediate patching of affected BlueZ versions, with administrators prioritizing updates to versions that contain fixed memory management routines in the sdp_cstate_alloc_buf function. System administrators should also implement network monitoring to detect unusual sdp packet patterns that may indicate exploitation attempts, and consider implementing rate limiting or connection filtering mechanisms to prevent continuous packet flooding. The vulnerability aligns with CWE-401, which specifically addresses memory leaks in software systems, and represents a typical example of how improper resource management can create persistent security weaknesses. From an ATT&CK framework perspective, this vulnerability could be categorized under privilege escalation and resource exhaustion techniques, as it allows attackers to consume system resources and potentially disrupt service availability. Organizations should also consider implementing intrusion detection systems that can identify abnormal Bluetooth service behavior patterns and establish baseline monitoring for memory usage trends to detect potential exploitation attempts before they result in service disruption.