CVE-2025-4397

Executive Summary

CVE-2025-4397 exposes a critical security flaw in the Medtronic MyCareLink Patient Monitor, a medical device used for remote patient monitoring. The vulnerability stems from the use of per-product credentials that are stored in a recoverable format (CWE-257). This allows an attacker with physical or local network access to extract these credentials and subsequently modify encrypted drive data, potentially compromising the integrity and confidentiality of patient monitoring data. The CVSS score of 6.8 reflects a high impact on confidentiality and integrity, though the attack vector is local, requiring some form of access to the device. No patch is currently available, and no public exploit code has been identified.

Supply Chain & Package Security

This vulnerability is not related to an open-source package (NPM, PyPI, Go, Ruby). It is a hardware/firmware issue specific to Medtronic's proprietary medical device ecosystem. The risk is primarily to healthcare organizations deploying these monitors in their networks.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Base Score: 6.8 (Medium)
• Attack Vector (AV): Local (L) – The attacker must have physical or logical access to the device.
• Attack Complexity (AC): Low (L) – No special conditions or mitigations are required.
• Privileges Required (PR): None (N) – No authentication is needed to exploit the credential storage.
• User Interaction (UI): None (N) – The victim does not need to perform any action.
• Scope (S): Unchanged (U) – The exploit does not affect other components beyond the vulnerable device.
• Confidentiality (C): High (H) – Encrypted drive data can be read.
• Integrity (I): High (H) – Encrypted drive data can be modified.
• Availability (A): High (H) – The device could be rendered inoperable or its data corrupted.

Threat Level: Medium. While the impact is severe, the local attack vector reduces the immediate exploitability in a remote context. However, in a healthcare environment, physical access to medical devices is a realistic threat.

Deep Dive & Mechanics

The vulnerability lies in how the Medtronic MyCareLink Patient Monitor stores credentials. Instead of using a unique, per-device secret or a hardware-backed keystore, the device uses a static set of credentials that are identical across all units of the same product line. These credentials are stored in a recoverable format (e.g., plaintext, reversible encryption, or a hardcoded string in firmware).

Attack Flow:

1. Reconnaissance: An attacker identifies a MyCareLink Patient Monitor on the network (e.g., via Shodan or local network scanning).
2. Access: The attacker gains physical access to the device (e.g., in a hospital room) or logical access via a compromised network segment.
3. Credential Extraction: The attacker extracts the stored credentials from the device's firmware, configuration files, or memory. This could involve:
   • Dumping the firmware via JTAG or UART.
   • Reading configuration files from the device's file system.
   • Analyzing the device's web interface or API responses.
4. Data Manipulation: Using the extracted credentials, the attacker mounts the encrypted drive and modifies patient data, device configuration, or logs. This could lead to:
   • Falsifying patient monitoring records.
   • Disabling alarms or safety features.
   • Installing persistent malware on the device.

Vulnerable vs. Patched Code

Since no patch is available, there is no patched code to compare. The vulnerable code is the credential storage mechanism within the device's firmware. A secure implementation would use:

• Unique per-device credentials generated at manufacturing time.
• Hardware Security Module (HSM) or Trusted Platform Module (TPM) to store keys.
• One-way hashing (e.g., bcrypt, Argon2) for any stored secrets.
• Encrypted storage with a key derived from a device-specific secret.

Example of Vulnerable Code (Conceptual):

// Vulnerable: Hardcoded credentials in firmware
char* username = "admin";
char* password = "Medtronic2023!";
// Stored in recoverable format (plaintext)

Example of Patched Code (Conceptual):

// Patched: Use device-specific key from TPM
uint8_t device_key[32];
tpm_get_random_key(device_key);
// Derive credentials from device_key
char* derived_password = derive_password(device_key);
// Store only a hash of the derived password
store_hash(hash_password(derived_password));

Exploitation & Lab Setup

Red Team (Offensive)

Objective: Extract credentials and modify encrypted drive data.

Lab Setup:

• Hardware: Medtronic MyCareLink Patient Monitor (physical device or emulator).
• Tools: JTAGulator, Bus Pirate, binwalk, firmware analysis tools (e.g., Ghidra, IDA Pro), and a hex editor.
• Network: Isolated lab network with the device connected.

Steps:

1. Firmware Dump:
   • Connect to the device's JTAG or UART interface.
   • Use openocd or a JTAGulator to dump the firmware flash.

   openocd -f interface/jtag.cfg -f target/medtronic.cfg -c "flash read_bank 0 firmware.bin 0x0 0x100000"
   

2. Credential Extraction:
   • Analyze the firmware with binwalk to extract filesystems.

   binwalk -e firmware.bin
   

   • Search for strings containing "password", "credential", or "key".

   strings firmware.bin | grep -i "password\|credential\|key"
   

3. Drive Mounting:
   • Use the extracted credentials to mount the encrypted drive (e.g., LUKS or BitLocker).

   cryptsetup luksOpen /dev/sdb1 encrypted_drive
   mount /dev/mapper/encrypted_drive /mnt
   

4. Data Modification:
   • Modify patient records or device configuration files.

   echo "Falsified data" > /mnt/patient_records.db
   

Blue Team (Defensive)

Objective: Detect and prevent exploitation.

Detection:

• Monitor for physical access attempts to medical devices (e.g., door alarms, camera feeds).
• Use network segmentation to isolate medical devices from general IT networks.
• Deploy host-based intrusion detection (HIDS) on the device if possible (e.g., OSSEC).
• Monitor for unusual file system access or process execution on the device.

Mitigation:

• Implement strict access controls to device interfaces (e.g., disable JTAG/UART in production).
• Use device attestation to verify firmware integrity.
• Apply the principle of least privilege for any credentials used by the device.

Indicators of Compromise (IOCs)

• Network:
  • Unusual SSH or Telnet connections to the device from non-medical IPs.
  • Traffic to known credential harvesting domains (e.g., pastebin.com, github.com).
• Host:
  • Presence of firmware.bin or dump.bin files on the device.
  • Modified configuration files (e.g., patient_records.db, device_config.xml).
  • New processes like cryptsetup, mount, or strings running on the device.
• Physical:
  • Signs of tampering with device casing or ports.
  • Unauthorized JTAG or UART connections.

Detection Engineering

YARA Rule

rule Medtronic_MyCareLink_Credential_Extraction {
    meta:
        description = "Detects attempts to extract credentials from Medtronic MyCareLink Patient Monitor firmware"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-4397"
    strings:
        $cred_string1 = "password" ascii wide nocase
        $cred_string2 = "credential" ascii wide nocase
        $cred_string3 = "Medtronic" ascii wide nocase
        $firmware_magic = { 1F 8B 08 00 } // gzip magic for firmware dumps
    condition:
        any of ($cred_string*) and $firmware_magic
}

Sigma Rule

title: Medtronic MyCareLink Credential Extraction Attempt
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects attempts to extract credentials from Medtronic MyCareLink Patient Monitor
author: Valters IT
date: 2025-04-10
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2025-4397
logsource:
    category: process_creation
    product: linux
detection:
    selection:
        Image|endswith:
            - '/bin/bash'
            - '/bin/sh'
        CommandLine|contains:
            - 'strings'
            - 'binwalk'
            - 'cryptsetup'
            - 'mount'
    condition: selection
falsepositives:
    - Legitimate firmware updates by authorized personnel
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"Medtronic MyCareLink Credential Exfiltration"; flow:to_server,established; content:"password"; nocase; content:"Medtronic"; nocase; distance:0; within:100; classtype:attempted-recon; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate Devices: Place MyCareLink Patient Monitors on a separate VLAN with strict firewall rules.
2. Disable Unused Interfaces: Physically disable JTAG, UART, and USB ports on the device.
3. Monitor Logs: Enable and monitor device logs for unauthorized access attempts.

Long-Term Fix:

• Vendor Patch: Await a firmware update from Medtronic that implements per-device credentials stored in a hardware-backed keystore.
• Device Replacement: If no patch is forthcoming, consider replacing the device with a more secure alternative.

Workaround:

• Network Segmentation: Use a dedicated network for medical devices with no direct internet access.
• Physical Security: Secure devices in locked cabinets or rooms.

Valters IT