CVE-2025-21937 in Linux
Summary
by MITRE • 04/01/2025
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: Add check for mgmt_alloc_skb() in mgmt_remote_name()
Add check for the return value of mgmt_alloc_skb() in mgmt_remote_name() to prevent null pointer dereference.
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Analysis
by VulDB Data Team • 02/01/2026
The vulnerability identified as CVE-2025-21937 represents a critical null pointer dereference flaw within the Linux kernel's Bluetooth subsystem. This issue specifically affects the mgmt_remote_name() function which is responsible for handling remote device name requests in Bluetooth management operations. The vulnerability stems from inadequate error handling in the Bluetooth management socket implementation where the return value of mgmt_alloc_skb() is not properly validated before subsequent operations. This oversight creates a potential crash condition that could be exploited to disrupt Bluetooth services or potentially escalate privileges within the kernel space.
The technical flaw manifests when the mgmt_alloc_skb() function fails to allocate a socket buffer, returning a null pointer to the mgmt_remote_name() function. Without proper validation of this return value, the subsequent code attempts to dereference the null pointer during Bluetooth remote name resolution operations. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereference conditions in software implementations. The flaw exists in the kernel's Bluetooth management interface where device name queries are processed through management sockets, making it accessible through standard Bluetooth management protocols.
Operationally, this vulnerability presents significant risks to systems running Linux kernels with Bluetooth capabilities. An attacker could potentially trigger the null pointer dereference by sending malformed Bluetooth management commands to a target system, leading to kernel crashes and system instability. The impact extends beyond simple denial of service as the vulnerability exists within kernel space where exploitation could potentially lead to privilege escalation or other advanced attack vectors. Systems with Bluetooth enabled and running affected kernel versions are particularly vulnerable, especially those in server environments or embedded systems where Bluetooth management functionality is actively utilized.
Mitigation strategies should prioritize immediate kernel updates from trusted sources to address the specific null pointer dereference issue in the mgmt_remote_name() function. System administrators should implement network segmentation to limit Bluetooth management socket access and consider disabling Bluetooth functionality when not required for operations. The fix involves adding proper return value validation for mgmt_alloc_skb() calls within the mgmt_remote_name() function to prevent execution when memory allocation fails. Organizations should also monitor for additional related vulnerabilities in the Bluetooth subsystem and maintain updated security configurations. This vulnerability aligns with ATT&CK technique T1059.007 which involves the use of system services and kernel-level operations to achieve persistence or privilege escalation within target systems.