CVE-2025-53477 is a NULL Pointer Dereference vulnerability identified in the Apache Mynewt NimBLE Bluetooth Low Energy (BLE) stack, affecting versions through 1.8.0. The root cause is missing validation checks on the Host Controller Interface (HCI) connection complete event or the HCI command transmit (TX) buffer. When asserts are disabled and the Bluetooth controller behaves incorrectly or is malformed (bogus), this can lead to dereferencing a NULL pointer, causing a crash or denial of service in the affected device. This vulnerability is categorized under CWE-476 (NULL Pointer Dereference). The flaw does not require user interaction but depends on the presence of a broken or malicious Bluetooth controller and disabled assert checks, which are typically enabled during development. Because of these constraints, the vulnerability's exploitation potential is limited, and no known exploits have been reported in the wild. The Apache Software Foundation has addressed this issue in NimBLE version 1.9.0, which includes proper validation to prevent NULL pointer dereference. NimBLE is widely used in embedded systems and IoT devices that require BLE connectivity, making this vulnerability relevant primarily to embedded device manufacturers and users. The vulnerability could cause device crashes or denial of service but does not directly expose sensitive data or allow code execution. The lack of a CVSS score suggests the need for a severity assessment based on impact and exploitability factors.

For European organizations, the impact of CVE-2025-53477 is primarily related to availability, as exploitation can cause device crashes or denial of service in embedded systems using Apache NimBLE. Confidentiality and integrity impacts are minimal since the vulnerability does not enable unauthorized data access or code execution. Organizations deploying IoT devices with BLE connectivity, especially those using Apache NimBLE versions up to 1.8.0, may experience service disruptions if devices encounter malformed Bluetooth controllers or if asserts are disabled in production firmware. This could affect operational continuity in industrial IoT, healthcare devices, or smart infrastructure relying on BLE communications. However, the requirement for a broken or bogus Bluetooth controller and disabled asserts reduces the likelihood of widespread exploitation. European manufacturers and integrators of BLE-enabled embedded devices should be aware of this vulnerability to avoid potential downtime or reliability issues. Failure to patch could lead to increased maintenance costs and reduced trust in device reliability, particularly in sectors with critical BLE-dependent systems.

1. Upgrade all Apache Mynewt NimBLE deployments to version 1.9.0 or later, where the vulnerability is fixed. 2. Ensure asserts are enabled in production firmware builds to detect and prevent NULL pointer dereferences during development and testing phases. 3. Validate and verify Bluetooth controller firmware and hardware to avoid malformed or bogus controllers that could trigger the vulnerability. 4. Implement robust input validation and error handling for HCI events in custom BLE stack integrations. 5. Conduct thorough testing of BLE-enabled devices under various Bluetooth controller conditions to detect potential crashes. 6. Monitor device logs and behavior for unexpected resets or crashes that could indicate exploitation attempts. 7. For manufacturers, incorporate secure development lifecycle practices focusing on embedded BLE stack security. 8. Maintain inventory of devices using NimBLE to prioritize patching and risk assessment. 9. Collaborate with Bluetooth controller vendors to ensure firmware integrity and compatibility. 10. Educate development teams about the risks of disabling asserts and the importance of defensive programming in embedded systems.