CVE-2025-4321 Overview
CVE-2025-4321 affects Bluetooth devices built with the Silicon Labs RS9116-WiseConnect SDK. The vulnerability allows an attacker within Bluetooth range to send malformed Logical Link Control and Adaptation Protocol (L2CAP) packets that put the target device into an unrecoverable state. Once triggered, the device stops responding to Bluetooth communications and requires a hard reset to restore normal operation. The flaw is categorized under [CWE-240], improper handling of inconsistent structural elements.
Critical Impact
An adjacent attacker can permanently disrupt Bluetooth functionality on affected devices until manual intervention restores service.
Affected Products
- Silicon Labs RS9116 Wi-Fi and Bluetooth modules
- WiseConnect SDK Bluetooth stack implementations
- Embedded IoT devices integrating the RS9116-WiseConnect SDK
Discovery Timeline
- 2025-11-17 - CVE-2025-4321 published to NVD
- 2026-06-17 - Last updated in NVD database
Technical Details for CVE-2025-4321
Vulnerability Analysis
The vulnerability resides in the L2CAP packet processing logic within the RS9116-WiseConnect SDK. L2CAP operates above the Host Controller Interface (HCI) and handles packet segmentation, reassembly, and channel multiplexing for Bluetooth communications. The SDK fails to properly validate structural fields in incoming L2CAP frames, classified under [CWE-240] as improper handling of inconsistent structural elements.
When the affected device processes a malformed L2CAP packet, internal state machines enter an inconsistent condition. The Bluetooth stack cannot recover through its normal error handling paths. Software-level recovery mechanisms such as connection teardown or stack restart do not restore functionality. Only a hard reset returns the device to operational status.
The impact is limited to availability. The advisory does not indicate confidentiality or integrity compromise, and no code execution or data exposure is associated with this flaw.
Root Cause
The root cause is insufficient validation of L2CAP packet fields during parsing. Structural inconsistencies such as invalid length fields, malformed channel identifiers, or unexpected control values are not rejected before they influence stack state.
Attack Vector
Exploitation requires Bluetooth radio proximity to the target. The attacker transmits crafted L2CAP frames over the air without authentication or user interaction. Any device within Bluetooth range of a vulnerable RS9116-based product can serve as the attack source. Refer to the Silicon Labs Community Post for vendor technical details.
Detection Methods for CVE-2025-4321
Indicators of Compromise
- Bluetooth-enabled devices that stop responding to pairing or data requests without an apparent software cause
- Repeated hard resets required to restore Bluetooth connectivity on RS9116-based products
- Unusual L2CAP traffic patterns captured by nearby Bluetooth sniffers prior to device failure
Detection Strategies
- Capture and inspect L2CAP traffic with Bluetooth protocol analyzers to identify malformed length fields and channel identifiers
- Correlate device unresponsiveness events with proximity-based wireless activity logs
- Monitor firmware watchdog and reset counters on fleet-managed IoT devices for anomalous reset frequency
Monitoring Recommendations
- Track Bluetooth connection stability metrics across deployed RS9116 devices
- Alert on devices requiring repeated power-cycle interventions within short time windows
- Maintain an inventory of products built on the WiseConnect SDK to scope monitoring coverage
How to Mitigate CVE-2025-4321
Immediate Actions Required
- Identify all deployed devices that integrate the RS9116-WiseConnect SDK Bluetooth stack
- Review the Silicon Labs Community Post for vendor guidance and updated SDK availability
- Restrict Bluetooth operation in high-risk environments until patched firmware is deployed
Patch Information
Silicon Labs has published guidance through its community portal. Operators should consult the Silicon Labs Community Post for the current SDK update addressing L2CAP packet validation. Firmware images built on vulnerable SDK versions must be rebuilt and redistributed to affected devices.
Workarounds
- Disable Bluetooth functionality on RS9116-based devices when not in active use
- Deploy affected devices only in physically controlled environments outside adjacent attacker range
- Implement automated remote reset capabilities to reduce recovery time when devices enter the unresponsive state
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
