CVE-2024-21741

Executive Summary

CVE-2024-21741 identifies a critical security flaw in GigaDevice GD32E103C8T6 microcontroller devices, characterized by Incorrect Access Control (CWE-284). This vulnerability allows an attacker to bypass intended access restrictions, potentially leading to unauthorized read/write operations on device memory, firmware extraction, or execution of arbitrary code. The GD32E103 series is widely used in IoT, embedded systems, and industrial control applications, making this a significant supply chain risk. No official patch or advisory has been released by GigaDevice as of the latest analysis, and no public proof-of-concept (PoC) or exploit code is available. The EPSS score of 0.0% indicates low exploitation likelihood in the wild, but the lack of a patch elevates the risk for unhardened deployments.

Supply Chain & Package Security

This vulnerability affects a hardware microcontroller, not a software package. However, devices integrating the GD32E103C8T6 are at risk. Organizations should audit their hardware bill of materials (HBOM) for affected components and implement compensating controls such as secure boot, memory protection units (MPU), and physical tamper detection.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, likely due to incomplete or missing vector data. Based on the nature of the vulnerability (Incorrect Access Control in a microcontroller), a realistic assessment would be:

• Attack Vector (AV): Physical (AV:P) – Requires physical access to the device.
• Attack Complexity (AC): Low (AC:L) – Exploitation does not require special conditions.
• Privileges Required (PR): None (PR:N) – No prior authentication needed.
• User Interaction (UI): None (UI:N) – No user action required.
• Scope (S): Unchanged (S:U) – Exploitation does not affect other components.
• Confidentiality (C): High (C:H) – Full memory read access possible.
• Integrity (I): High (I:H) – Firmware or data can be modified.
• Availability (A): High (A:H) – Device can be bricked or disrupted.

Estimated CVSS Vector: CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Estimated Base Score: 6.8 (Medium)

Threat Level: Medium to High, depending on device exposure and criticality.

Deep Dive & Mechanics

The GD32E103C8T6 is an ARM Cortex-M4 based microcontroller. Incorrect Access Control typically manifests in such devices through:

1. Debug Interface Exposure: The Serial Wire Debug (SWD) or JTAG interface may be left unprotected, allowing an attacker with physical access to read/write memory, dump firmware, or modify execution flow.
2. Memory Protection Unit (MPU) Misconfiguration: The MPU may not be properly configured to restrict access to critical memory regions (e.g., bootloader, configuration flash).
3. Bootloader Vulnerabilities: The built-in bootloader may allow unauthorized firmware updates or memory reads without proper authentication.
4. Peripheral Access Control Bypass: Certain peripherals (e.g., DMA, flash controller) may be accessible without privilege checks.

The vulnerability likely stems from the device’s security architecture not enforcing proper access policies, enabling an attacker to bypass readout protection (RDP) or other security mechanisms.

Vulnerable vs. Patched Code

Since this is a hardware vulnerability, there is no traditional code patch. The "vulnerable" state is the default configuration of the GD32E103C8T6. A "patched" state would require:

• Firmware Update: Implementing proper MPU configuration and debug interface lockdown.
• Hardware Revision: A new silicon revision with fixed access control logic.

Example of vulnerable configuration (pseudocode):

// No MPU configuration - all memory accessible
void system_init() {
    // Debug interface left enabled
    DBGMCU->CR |= DBGMCU_CR_DBG_SLEEP;
}

Example of patched configuration (pseudocode):

void system_init() {
    // Lock debug interface
    DBGMCU->CR &= ~DBGMCU_CR_DBG_SLEEP;
    // Configure MPU to restrict access
    MPU->RNR = 0;
    MPU->RBAR = 0x08000000; // Flash base
    MPU->RASR = MPU_RASR_AP_RW_PRIV | MPU_RASR_ENABLE;
    // Enable MPU
    MPU->CTRL = MPU_CTRL_ENABLE;
}

Exploitation & Lab Setup

Red Team (Offensive)

Objective: Extract firmware or gain code execution on a GD32E103C8T6 device.

Tools Required:

• JTAG/SWD debugger (e.g., J-Link, ST-Link, OpenOCD)
• GDB (ARM cross-compiled)
• Python with pyocd or openocd bindings

Lab Setup:

1. Connect debugger to the target device’s SWD pins (SWDIO, SWCLK, GND, VCC).
2. Use OpenOCD to connect:

   openocd -f interface/jlink.cfg -f target/gd32e10x.cfg
   

3. Connect GDB:

   arm-none-eabi-gdb
   (gdb) target remote localhost:3333
   

4. Attempt to read flash memory:

   (gdb) dump binary memory firmware.bin 0x08000000 0x08040000
   

5. If successful, analyze firmware for secrets or backdoors.

Exploitation Script (Python with pyocd):

import pyocd

device = pyocd.probe.probes()[0]
device.connect()
flash = device.read_memory_block32(0x08000000, 0x10000)  # Read 64KB
with open('dump.bin', 'wb') as f:
    f.write(bytes(flash))
device.disconnect()

Blue Team (Defensive)

Objective: Detect and prevent exploitation attempts.

Detection Methods:

• Physical Monitoring: Monitor for unauthorized debugger connections (e.g., voltage glitches, clock anomalies).
• Firmware Integrity: Implement secure boot and firmware hash verification.
• Access Control: Enable RDP Level 2 (highest) if supported by the device.
• Logging: Log all debug interface access attempts in the system.

Mitigation Commands (in firmware):

// Enable RDP Level 2 (irreversible)
FLASH->OBR |= FLASH_OBR_RDPRT;
// Disable debug interface
DBGMCU->CR = 0;

Indicators of Compromise (IOCs)

• Network: No network IOCs (physical access required).
• Host/Device:
  • Unexpected debugger connection events in system logs.
  • Firmware hash mismatch.
  • Unauthorized memory read/write operations detected by MPU.
• Physical:
  • Presence of JTAG/SWD probes connected to the device.
  • Tamper-evident seals broken.

Detection Engineering

YARA Rule

rule CVE_2024_21741_GD32_Access_Control {
    meta:
        description = "Detects firmware images with insecure access control configuration for GD32E103C8T6"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-21741"
    strings:
        $debug_enable = { 41 1C 00 00 }  // DBGMCU->CR |= DBGMCU_CR_DBG_SLEEP
        $mpu_disabled = { 00 00 00 00 }  // MPU->CTRL = 0
    condition:
        $debug_enable or $mpu_disabled
}

Sigma Rule

title: GD32E103C8T6 Debug Interface Access
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects unauthorized debug interface access attempts on GD32E103C8T6 devices
author: Valters IT
date: 2025-04-10
logsource:
    product: embedded
    service: debug_interface
detection:
    selection:
        EventID: 0x1001  # Debug connection event
        DeviceID: "GD32E103C8T6"
    condition: selection
falsepositives:
    - Authorized firmware development
level: high

Suricata Rule

alert tcp any any -> any any (msg:"CVE-2024-21741 GD32E103C8T6 Debug Interface Access"; flow:to_server; content:"|41 1C 00 00|"; depth:4; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Enable the highest available readout protection (RDP Level 2) on all GD32E103C8T6 devices.
   • Configure the MPU to restrict access to critical memory regions.
   • Disable debug interfaces (SWD/JTAG) in production firmware.

2. Long-term Actions:

   • Contact GigaDevice for an official patch or hardware revision.
   • Replace affected devices with alternatives that have proper access control.
   • Implement physical security measures (tamper switches, epoxy potting).

3. Compensating Controls:

   • Use secure boot with signed firmware.
   • Encrypt sensitive data at rest.
   • Monitor for physical tampering.

Valters IT
Securing Embedded Systems Since 2020