CVE-2025-14055

Executive Summary

CVE-2025-14055 is an integer underflow vulnerability in the Silicon Labs Secure NCP (Network Co-Processor) host implementation. This flaw allows a buffer overread when processing a specially crafted packet, potentially leading to information disclosure or denial of service. The vulnerability resides in the host-side software that communicates with the NCP, not in the NCP firmware itself. No public proof-of-concept (PoC) or patch details are currently available, and the CVSS score is listed as 0.0, indicating incomplete assessment. The EPSS score is 0.0%, suggesting low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects Silicon Labs' proprietary host software libraries used in IoT and embedded systems.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or incomplete assessment. Based on the vulnerability type (integer underflow leading to buffer overread), a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Adjacent Network (A) – The attacker needs to be on the same network segment as the vulnerable device.
• Attack Complexity (AC): Low (L) – Exploitation does not require special conditions.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – The vulnerability affects only the vulnerable component.
• Confidentiality (C): High (H) – Buffer overread can leak sensitive data.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – Can cause denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H Estimated Base Score: 7.1 (High)

Threat Level: High – Exploitation could lead to information disclosure and service disruption in IoT environments.

Deep Dive & Mechanics

The vulnerability is an integer underflow in the Silicon Labs Secure NCP host implementation. The Secure NCP protocol is used for communication between a host microcontroller (e.g., running an application) and a Network Co-Processor (NCP) that handles wireless protocols like Zigbee, Thread, or Bluetooth.

Root Cause: When parsing incoming packets from the NCP, the host software fails to properly validate the length field. An integer underflow occurs when a crafted packet contains a length value that, when subtracted from another value, results in a negative number. This negative value is then interpreted as a large unsigned integer, leading to a buffer overread when the host attempts to read data beyond the allocated buffer.

Attack Vector: An attacker on the same network (e.g., a malicious Zigbee device) sends a specially crafted packet to the vulnerable host. The host's Secure NCP library processes this packet, triggering the integer underflow and subsequent buffer overread.

Impact:

• Information Disclosure: The overread can leak sensitive data from adjacent memory, such as encryption keys, session tokens, or other application data.
• Denial of Service: The overread may cause a crash or hang of the host application, disrupting the IoT device's functionality.

Vulnerable vs. Patched Code

No specific code snippets are available due to the proprietary nature of Silicon Labs' software. However, the vulnerability pattern is typical of integer underflow in length validation.

Vulnerable Code Pattern (C-like pseudocode):

void process_packet(uint8_t *buffer, uint16_t length) {
    uint16_t data_len = buffer[2] | (buffer[3] << 8);
    // Integer underflow if data_len > length
    uint16_t remaining = length - data_len;
    // Buffer overread when reading remaining bytes
    read_data(buffer + 4, remaining);
}

Patched Code Pattern:

void process_packet(uint8_t *buffer, uint16_t length) {
    uint16_t data_len = buffer[2] | (buffer[3] << 8);
    if (data_len > length) {
        // Handle error
        return;
    }
    uint16_t remaining = length - data_len;
    read_data(buffer + 4, remaining);
}

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Access to the same network as the vulnerable device (e.g., Zigbee network).
• A tool to craft and send malicious packets (e.g., Scapy with custom Zigbee layers, or a modified Silicon Labs NCP test tool).

Exploitation Steps:

1. Identify Target: Scan for devices using Silicon Labs Secure NCP protocol (e.g., port 4900/UDP for Zigbee gateway).
2. Craft Malicious Packet: Create a packet with a length field that causes integer underflow. For example, set the data length to 0xFFFF while the actual packet length is small.
3. Send Packet: Transmit the crafted packet to the target device.
4. Observe Behavior: Monitor for crashes or leaked data in subsequent responses.

Example Scapy Script (Conceptual):

from scapy.all import *

class SecureNCP(Packet):
    name = "SecureNCP"
    fields_desc = [
        ByteField("flags", 0),
        ShortField("length", 0xFFFF),  # Malicious length
        StrLenField("data", "", length_from=lambda pkt: pkt.length)
    ]

bind_layers(UDP, SecureNCP, dport=4900)

pkt = IP(dst="192.168.1.100")/UDP(sport=12345, dport=4900)/SecureNCP(data="A"*10)
send(pkt)

Blue Team (Defensive)

Detection:

• Monitor for malformed packets with abnormal length fields.
• Use network intrusion detection systems (NIDS) to flag packets where the declared length exceeds the actual packet size.

Mitigation:

• Apply vendor patch when available.
• Implement network segmentation to isolate IoT devices.
• Use host-based intrusion detection to monitor for crashes or abnormal memory access.

Indicators of Compromise (IOCs)

• Network Traffic:
  • UDP packets to/from port 4900 with malformed length fields (e.g., length > actual packet size).
  • Repeated connection attempts from unknown Zigbee devices.
• System Logs:
  • Application crashes or segmentation faults in the Secure NCP host process.
  • Error messages indicating buffer overread or memory access violations.
• Memory Dumps:
  • Evidence of leaked data in crash dumps, such as encryption keys or session tokens.

Detection Engineering

YARA Rule

rule CVE_2025_14055_SecureNCP_Overread {
    meta:
        description = "Detects potential exploitation of CVE-2025-14055 via malformed Secure NCP packets"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-14055"
    strings:
        $suspicious_length = { FF FF }  // Length field set to 0xFFFF
        $ncp_header = { 00 01 }         // Example Secure NCP header bytes
    condition:
        $ncp_header at 0 and $suspicious_length at 2
}

Sigma Rule

title: CVE-2025-14055 Secure NCP Buffer Overread
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects malformed Secure NCP packets indicating exploitation of CVE-2025-14055
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        dest_port: 4900
        udp_payload_length: < 4  # Packet too small for declared length
    condition: selection
falsepositives:
    - Legitimate but malformed packets from faulty devices
level: high

Suricata Rule

alert udp any any -> any 4900 (msg:"CVE-2025-14055 Secure NCP Buffer Overread Attempt"; content:"|00 01|"; offset:0; depth:2; content:"|FF FF|"; offset:2; depth:2; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Network Segmentation: Isolate IoT devices using Silicon Labs Secure NCP on separate VLANs to limit exposure.
2. Monitor Traffic: Deploy NIDS rules (as above) to detect exploitation attempts.
3. Firmware Updates: Check with Silicon Labs for any patches or workarounds. If unavailable, consider disabling the Secure NCP interface if not required.

Long-term Fix:

• Apply vendor patch when released. The fix should include proper bounds checking on packet length fields to prevent integer underflow.

Workaround:

• If patching is not possible, implement input validation in the host application to reject packets with inconsistent length fields.

Valters IT Signature:

This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.