CVE-2025-52435 Overview
CVE-2025-52435 is a cryptographic vulnerability in Apache NimBLE, an open-source Bluetooth Low Energy (BLE) stack. The vulnerability stems from improper handling of the Pause Encryption procedure on the Link Layer, which can result in a previously encrypted Bluetooth connection being left in an unencrypted state. This allows eavesdroppers within radio range to observe the remainder of the Bluetooth communication exchange in cleartext.
Critical Impact
Sensitive data transmitted over Bluetooth connections using affected Apache NimBLE versions may be exposed to eavesdroppers, potentially compromising confidential communications, authentication data, and other sensitive information exchanged between BLE devices.
Affected Products
- Apache NimBLE versions through 1.8.0 and earlier
- Devices and applications utilizing the Apache MyNewt NimBLE Bluetooth stack
- IoT devices and embedded systems implementing NimBLE for BLE communications
Discovery Timeline
- January 8, 2026 - Vulnerability disclosed via Openwall OSS Security Post
- January 10, 2026 - CVE-2025-52435 published to NVD
- January 13, 2026 - Last updated in NVD database
Technical Details for CVE-2025-52435
Vulnerability Analysis
This vulnerability is classified as CWE-5 (J2EE Misconfiguration: Data Transmission Without Encryption). The flaw exists in the Bluetooth Link Layer encryption handling within Apache NimBLE. When the Pause Encryption procedure is invoked during an active BLE connection, the implementation fails to properly restore the encrypted state afterward, leaving the connection unencrypted for all subsequent data exchanges.
The attack can be exploited over the network without requiring user interaction or prior authentication. While the vulnerability does not allow attackers to modify data (integrity is preserved) or cause service disruptions (availability is unaffected), it provides complete confidentiality compromise for data transmitted after the encryption failure occurs.
Root Cause
The root cause lies in the improper state management during the Pause Encryption procedure at the Link Layer level. When encryption is paused for legitimate protocol operations, the NimBLE stack fails to re-establish the encrypted communication channel. This leaves a timing window where the connection transitions from encrypted to unencrypted without proper restoration, violating the expected security guarantees of BLE encrypted communications.
Attack Vector
An attacker positioned within Bluetooth radio range (typically 10-100 meters depending on device class) can passively monitor BLE communications. By waiting for or potentially triggering a Pause Encryption event, the attacker gains the ability to capture all subsequent traffic in plaintext. This is particularly concerning in scenarios involving:
- Medical devices transmitting patient health data
- Industrial IoT sensors exchanging operational data
- Smart home devices communicating with controllers
- Wearable devices syncing personal information
The attack is passive in nature, meaning it leaves no traces on the target devices and is difficult to detect through conventional monitoring.
Detection Methods for CVE-2025-52435
Indicators of Compromise
- Unexpected unencrypted BLE traffic following established encrypted connections
- BLE connection encryption status changes without corresponding application-level requests
- Anomalous Pause Encryption procedure calls in BLE protocol traces
- Bluetooth packet captures showing cleartext data on connections that should be encrypted
Detection Strategies
- Implement BLE traffic analysis to monitor for encryption state transitions
- Deploy Bluetooth protocol analyzers to detect unencrypted data following established encrypted sessions
- Audit firmware versions on IoT devices and embedded systems using NimBLE
- Perform security assessments on BLE implementations to verify encryption persistence
Monitoring Recommendations
- Enable detailed logging on BLE controllers to track encryption state changes
- Monitor for security advisories from Apache regarding NimBLE updates
- Implement network segmentation to limit BLE device exposure
- Conduct regular firmware inventory audits to identify devices running vulnerable NimBLE versions
How to Mitigate CVE-2025-52435
Immediate Actions Required
- Upgrade Apache NimBLE to version 1.9.0 or later immediately
- Audit all deployed devices and applications using NimBLE for affected versions
- Implement physical security controls to limit unauthorized Bluetooth access in sensitive areas
- Consider disabling BLE functionality on critical systems until patches can be applied
Patch Information
Apache has released version 1.9.0 of NimBLE which addresses this vulnerability. The fix is available through the official Apache MyNewt NimBLE repository. Two commits have been provided to address the issue:
Additional details are available via the Apache Mailing List Discussion.
Workarounds
- Implement application-layer encryption (e.g., TLS) for sensitive data transmitted over BLE as a defense-in-depth measure
- Reduce Bluetooth transmission power to limit the physical range available to potential eavesdroppers
- Deploy BLE communications only in physically controlled environments until patching is complete
- Consider alternative secure communication protocols if BLE patching is not immediately feasible
# Verify NimBLE version in your project dependencies
cd /path/to/mynewt-project
newt info | grep nimble
# Update NimBLE to patched version
newt upgrade apache-mynewt-nimble
newt target set myapp nimble_version=1.9.0
newt build myapp
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
