CVE-2025-52435 identifies a security vulnerability in the Apache Mynewt NimBLE stack, versions up to and including 1.8.0. NimBLE is an open-source Bluetooth Low Energy (BLE) protocol stack used in embedded and IoT devices. The vulnerability arises from improper handling of the Pause Encryption procedure at the Link Layer, a critical phase in BLE communications where encryption can be temporarily suspended. Specifically, when the Pause Encryption command is processed, the connection remains in an unencrypted state afterward, despite previously being encrypted. This misconfiguration is classified under CWE-5, indicating data transmission without encryption due to improper configuration. The consequence is that an attacker with the capability to eavesdrop on the BLE radio frequency can intercept and observe all subsequent data exchanged over the connection in plaintext. This undermines the confidentiality guarantees of BLE communications, potentially exposing sensitive information transmitted between devices. The vulnerability does not require user interaction or authentication to be exploited, increasing its risk profile. Apache has addressed this issue in version 1.9.0 of NimBLE, which corrects the encryption state handling to ensure that paused encryption does not leave the connection unprotected. No public exploits have been reported to date, but the flaw poses a significant risk to devices relying on NimBLE for secure BLE communications, especially in environments where sensitive data is transmitted. The vulnerability highlights the importance of correct encryption state management in BLE stacks and the risks posed by misconfigurations in embedded protocol implementations.

For European organizations, the vulnerability presents a significant confidentiality risk, particularly for industries relying on BLE-enabled IoT devices, such as healthcare, manufacturing, smart buildings, and automotive sectors. Data transmitted over BLE connections that use affected NimBLE versions can be intercepted by attackers within radio range, potentially exposing sensitive operational or personal data. This could lead to breaches of privacy regulations such as GDPR if personal data is compromised. Additionally, industrial control systems or medical devices using NimBLE could have their communications intercepted, leading to operational disruptions or safety concerns. The lack of encryption also increases the risk of further attacks, such as replay or man-in-the-middle attacks, if attackers can manipulate the unencrypted traffic. The vulnerability may undermine trust in BLE-based solutions and require costly audits and remediation efforts. Given the widespread adoption of BLE in consumer and industrial devices, the scope of impact is broad, affecting device manufacturers, service providers, and end-users across Europe.

The primary mitigation is to upgrade Apache Mynewt NimBLE to version 1.9.0 or later, where the encryption pause handling is corrected. Organizations should audit all BLE-enabled devices and firmware to identify those using vulnerable NimBLE versions. For devices that cannot be immediately upgraded, consider disabling BLE communications or restricting their use to trusted environments to reduce exposure. Implement network segmentation and RF shielding where possible to limit attacker proximity. Monitor BLE traffic for anomalies that may indicate interception attempts. Device manufacturers should review their BLE stack configurations to ensure encryption is never left paused or disabled unintentionally. Security teams should incorporate BLE encryption state checks into their device security assessments and penetration tests. Finally, organizations should maintain an inventory of BLE devices and enforce strict patch management policies to promptly address such vulnerabilities in embedded components.