CVE-2025-38641 in Linux
Summary
by MITRE • 08/22/2025
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: btusb: Fix potential NULL dereference on kmalloc failure
Avoid potential NULL pointer dereference by checking the return value of kmalloc and handling allocation failure properly.
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Analysis
by VulDB Data Team • 05/28/2026
This vulnerability resides within the Linux kernel's Bluetooth subsystem, specifically affecting the btusb driver module responsible for USB-based Bluetooth communication. The flaw represents a classic null pointer dereference issue that occurs when memory allocation fails during kernel operation. The vulnerability manifests when the kmalloc function, which is used to allocate memory in kernel space, returns a NULL pointer due to insufficient memory resources. This NULL return value is not properly checked before being dereferenced, creating a potential system crash or exploitation vector.
The technical implementation of this vulnerability stems from inadequate error handling within the btusb driver's memory management routines. When the driver attempts to allocate memory for Bluetooth packet processing or device state management, the kmalloc call may fail due to memory exhaustion or allocation constraints typical in embedded or resource-constrained environments. The driver's failure to validate the kmalloc return value before proceeding with memory operations creates a path where a NULL pointer is dereferenced, leading to kernel oops or system instability. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a fundamental memory safety issue that has been a persistent concern in kernel-level programming.
The operational impact of this vulnerability extends beyond simple system crashes, potentially enabling privilege escalation or denial of service attacks in environments where Bluetooth functionality is actively used. Attackers could exploit this weakness by forcing memory allocation failures through resource exhaustion techniques or by triggering specific Bluetooth communication patterns that cause the driver to attempt allocations that fail. The vulnerability affects systems running Linux kernels where the btusb driver is loaded and active, particularly those with USB Bluetooth adapters or embedded systems that rely on kernel Bluetooth functionality. This issue aligns with ATT&CK technique T1059.003 for kernel-mode rootkits and T1499.004 for network denial of service, as it can be leveraged to destabilize system operations or create persistent access points.
Mitigation strategies for this vulnerability require immediate kernel updates from vendors that include the patched btusb driver implementation. System administrators should prioritize applying security patches that properly validate kmalloc return values and implement graceful failure handling mechanisms. The fix typically involves adding null pointer checks immediately after memory allocation calls, ensuring that the driver transitions to safe states when allocation fails rather than proceeding with invalid memory references. Additionally, monitoring systems should be configured to detect unusual memory allocation patterns or kernel oops events that may indicate exploitation attempts. Organizations should also implement proper resource management practices, including memory pressure monitoring and allocation failure logging, to detect potential exploitation attempts. The vulnerability demonstrates the critical importance of defensive programming practices in kernel space, where memory allocation failures must always be handled gracefully to prevent system instability or security breaches.