CVE-2023-53827 in Linux
Summary
by MITRE • 12/09/2025
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: L2CAP: Fix use-after-free in l2cap_disconnect_{req,rsp}
Similar to commit d0be8347c623 ("Bluetooth: L2CAP: Fix use-after-free caused by l2cap_chan_put"), just use l2cap_chan_hold_unless_zero to prevent referencing a channel that is about to be destroyed.
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Analysis
by VulDB Data Team • 03/30/2026
The vulnerability CVE-2023-53827 represents a critical use-after-free condition within the Linux kernel's Bluetooth Low Energy implementation, specifically affecting the L2CAP (Logical Link Control and Adaptation Protocol) layer. This flaw exists in the Bluetooth subsystem where the kernel handles connection management between Bluetooth devices, particularly during disconnection sequences. The vulnerability arises from improper reference management during the l2cap_disconnect_req and l2cap_disconnect_rsp operations, creating a window where memory structures could be freed while still being referenced by ongoing processes.
The technical root cause stems from a race condition in channel reference counting mechanisms within the Bluetooth L2CAP implementation. When a disconnection request or response is processed, the kernel fails to properly maintain channel references, allowing a scenario where a channel structure might be deallocated while another process still holds a reference to it. This pattern mirrors a previously identified vulnerability described in commit d0be8347c623, indicating a consistent pattern of reference management flaws within the Bluetooth subsystem. The vulnerability manifests when l2cap_chan_put is called without proper safeguards to prevent accessing memory that has already been freed, creating potential for arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling privilege escalation attacks or denial of service conditions that could affect any system running a Linux kernel with Bluetooth capabilities. An attacker positioned within range of a vulnerable Bluetooth device could exploit this condition to execute malicious code with kernel privileges, particularly affecting systems where Bluetooth is enabled and actively used. The vulnerability affects systems with Bluetooth Low Energy support, including smartphones, laptops, IoT devices, and embedded systems that utilize the Linux kernel's Bluetooth stack. The risk is amplified in environments where Bluetooth services are continuously running or where automatic connection attempts occur, as the window for exploitation increases with system activity.
Mitigation strategies focus on implementing proper reference counting mechanisms and ensuring that channel structures remain valid throughout the disconnection process. The fix implemented addresses this by incorporating l2cap_chan_hold_unless_zero function calls to prevent referencing channels that are about to be destroyed, effectively closing the race condition window. System administrators should prioritize applying kernel updates that contain this fix, particularly in environments where Bluetooth services are actively utilized. Organizations should also implement monitoring for unusual Bluetooth activity patterns that could indicate exploitation attempts, and consider disabling Bluetooth services when not actively needed. The vulnerability aligns with CWE-416, which addresses use-after-free conditions, and represents a potential ATT&CK technique under T1059 for privilege escalation through kernel exploits. Regular security audits of Bluetooth subsystems and kernel updates form essential components of defense-in-depth strategies to protect against similar vulnerabilities that may emerge from complex reference management in kernel space.