CVE-2025-53477 is a NULL Pointer Dereference vulnerability identified in Apache Mynewt NimBLE, an open-source Bluetooth Low Energy (BLE) stack maintained by the Apache Software Foundation. The vulnerability stems from insufficient validation of the Host Controller Interface (HCI) connection complete event or the HCI command transmit (TX) buffer. Specifically, when asserts are disabled and the Bluetooth controller behaves incorrectly or maliciously (e.g., sending broken or bogus HCI packets), the software dereferences a NULL pointer. This leads to a denial of service (DoS) condition by crashing or halting the BLE stack operation. The flaw affects all versions of Apache NimBLE up to and including 1.8.0. The issue is resolved in version 1.9.0, which includes proper validation and error handling to prevent NULL pointer dereference. The vulnerability has a CVSS v3.1 base score of 7.5, indicating a high severity due to its network attack vector, low attack complexity, no required privileges or user interaction, and a high impact on availability. However, exploitation is constrained by the need for disabled asserts and a compromised or faulty Bluetooth controller, which reduces the likelihood of widespread exploitation. No known exploits have been reported in the wild to date. This vulnerability primarily threatens embedded systems and IoT devices that rely on Apache NimBLE for BLE communications, potentially causing device crashes or service interruptions.

For European organizations, the primary impact of CVE-2025-53477 is the potential denial of service in devices using Apache NimBLE for Bluetooth Low Energy communications. This can disrupt critical IoT deployments, industrial automation systems, healthcare devices, and consumer electronics that rely on BLE connectivity. Service interruptions could lead to operational downtime, loss of data transmission, and degraded user experience. In sectors such as manufacturing, smart cities, and healthcare, where BLE-enabled devices are integral, this could affect safety, monitoring, and control systems. Although the vulnerability does not compromise confidentiality or integrity, the availability impact is significant, especially in environments where BLE devices perform essential functions. The requirement for a broken or malicious Bluetooth controller limits the risk but does not eliminate it, particularly in scenarios where attackers have physical proximity or supply chain access. European organizations with large-scale BLE deployments should assess their exposure and prioritize patching to maintain service continuity and device reliability.

To mitigate CVE-2025-53477, European organizations should: 1) Upgrade all Apache NimBLE instances to version 1.9.0 or later, where the vulnerability is fixed. 2) Implement strict supply chain controls to ensure Bluetooth controllers are authentic and uncompromised, reducing the risk of malicious or faulty devices triggering the flaw. 3) Enable asserts during development and testing phases to detect abnormal behavior early. 4) Monitor BLE device logs and system stability for signs of crashes or unexpected resets that could indicate exploitation attempts. 5) Employ network segmentation and access controls to limit exposure of BLE devices to untrusted networks or actors. 6) Conduct regular firmware and software audits on BLE-enabled devices to ensure timely application of security patches. 7) Educate technical staff on the specific risks associated with BLE stack vulnerabilities and the importance of maintaining updated software. These targeted actions go beyond generic advice by focusing on the unique exploitation conditions and operational context of Apache NimBLE deployments.