CVE-2024-36419

Executive Summary

CVE-2024-36419 is a Host Header Injection vulnerability affecting SuiteCRM, an open-source Customer Relationship Management (CRM) application. The flaw exists in versions prior to 8.6.1 and is triggered when an attacker directly accesses the /legacy route. By manipulating the Host header in an HTTP request, an attacker can inject arbitrary values that may be used in server-side redirects or link generation, potentially leading to phishing attacks or cache poisoning. The vulnerability has a CVSS score of 4.3 (Medium) and a low EPSS score of 0.0%, indicating limited active exploitation in the wild. No public proof-of-concept (PoC) code or exploit templates are currently available. The vendor has released a patch in version 8.6.1.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) but is a direct application-level flaw in the SuiteCRM codebase. Organizations using SuiteCRM should treat this as a critical update for their deployment.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N
• Base Score: 4.3 (Medium)
• Attack Vector (AV): Network (N) – Exploitable remotely.
• Attack Complexity (AC): Low (L) – No special conditions required.
• Privileges Required (PR): None (N) – No authentication needed.
• User Interaction (UI): Required (R) – Victim must click a crafted link or visit a malicious page.
• Scope (S): Unchanged (U) – Impact confined to the vulnerable component.
• Confidentiality Impact (C): None (N) – No data exposure.
• Integrity Impact (I): Low (L) – Possible manipulation of redirects or links.
• Availability Impact (A): None (N) – No denial of service.

Threat Level: Medium. The requirement for user interaction and the lack of public exploits reduce immediate risk, but the vulnerability can be chained with other attacks (e.g., cache poisoning) to increase impact.

Deep Dive & Mechanics

The vulnerability resides in SuiteCRM’s handling of the /legacy route. When a request is made to this endpoint, the application constructs redirect URLs or generates links using the value of the Host header without proper validation. An attacker can supply a malicious Host header (e.g., evil.com) to cause the server to redirect users to an attacker-controlled domain or to generate links that point to malicious sites.

Root Cause: Insufficient input sanitization of the Host header in the legacy route handler. The application trusts the header value for constructing URLs, allowing injection of arbitrary hostnames.

Attack Scenario:

1. An attacker crafts a link to a legitimate SuiteCRM instance: https://victim-crm.com/legacy.
2. The attacker intercepts or modifies the request to include a malicious Host header: Host: evil.com.
3. The SuiteCRM server processes the request and generates a redirect or link using the injected host.
4. A victim clicking the link is redirected to evil.com, where a phishing page or malware is hosted.

Impact: Phishing, session hijacking, cache poisoning, and bypass of security controls that rely on host validation.

Vulnerable vs. Patched Code

Vulnerable Code (Pre-8.6.1): The legacy route handler likely uses $_SERVER['HTTP_HOST'] directly without validation:

// Vulnerable example
$host = $_SERVER['HTTP_HOST'];
$redirect_url = "http://" . $host . "/some/path";
header("Location: " . $redirect_url);

Patched Code (8.6.1+): The patch introduces validation to ensure the Host header matches an allowed list or is sanitized:

// Patched example
$allowed_hosts = ['victim-crm.com', 'admin.victim-crm.com'];
$host = $_SERVER['HTTP_HOST'];
if (in_array($host, $allowed_hosts)) {
    $redirect_url = "http://" . $host . "/some/path";
    header("Location: " . $redirect_url);
} else {
    // Log or reject
    header("HTTP/1.1 400 Bad Request");
    exit;
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• A vulnerable SuiteCRM instance (version < 8.6.1).
• Ability to intercept and modify HTTP requests (e.g., Burp Suite, cURL).

Exploitation Steps:

1. Identify the target SuiteCRM URL: https://target-crm.com/legacy.
2. Send a crafted request with a malicious Host header:

   curl -H "Host: attacker.com" https://target-crm.com/legacy
   

3. Observe the response. If the server redirects to attacker.com, the vulnerability is confirmed.
4. For phishing, craft a link that includes the malicious host:

   <a href="https://target-crm.com/legacy">Click here</a>
   

   The victim’s browser will follow the redirect to attacker.com.

Note: No public exploit code is available. The above steps demonstrate the core injection.

Blue Team

Detection:

• Monitor for unusual Host headers in HTTP requests, especially to /legacy endpoints.
• Look for redirect responses (3xx) to unexpected domains.
• Use the detection rules below.

Mitigation:

• Immediately upgrade to SuiteCRM 8.6.1 or later.
• Implement a Web Application Firewall (WAF) rule to block requests with suspicious Host headers.
• Validate the Host header against a whitelist of allowed domains at the server level (e.g., Apache/Nginx configuration).

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP requests to /legacy with a Host header not matching the legitimate domain.
  • Redirect responses (HTTP 301/302) to external domains.
• Log IOCs:
  • Server logs showing Host header values like evil.com, phishing.net, or other suspicious domains.
  • Repeated requests to /legacy from a single IP with varying Host headers.
• File IOCs:
  • Modified SuiteCRM files (if attacker gains access) – check integrity of legacy route handler.

Detection Engineering

YARA Rule

rule CVE_2024_36419_Host_Header_Injection {
    meta:
        description = "Detects Host Header Injection attempts against SuiteCRM /legacy route"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-36419"
    strings:
        $host_header = /Host:\s*(?!victim-crm\.com)[^\r\n]+/ nocase
        $legacy_route = "/legacy"
    condition:
        $legacy_route and $host_header
}

Sigma Rule

title: SuiteCRM Host Header Injection Attempt
id: 8f3a2b1c-5d6e-7f8a-9b0c-1d2e3f4a5b6c
status: experimental
description: Detects HTTP requests to SuiteCRM /legacy route with suspicious Host headers
author: Valters IT
logsource:
    category: webserver
    product: apache
    service: access_combined
detection:
    selection:
        cs-uri-stem: "/legacy"
        cs-host:
            - "evil.com"
            - "phishing.net"
            - "malicious.org"
    condition: selection
falsepositives:
    - Legitimate redirects to subdomains
level: medium

Suricata Rule

alert http any any -> any any (msg:"CVE-2024-36419 SuiteCRM Host Header Injection"; flow:to_server; content:"/legacy"; http_uri; content:"Host|3a|"; http_header; pcre:"/Host:\s*(?!victim-crm\.com)[^\r\n]+/i"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Upgrade SuiteCRM to version 8.6.1 or later. This is the only complete fix.
2. Apply a WAF rule to block requests with Host headers not matching the expected domain.
3. Validate Host header at the server level (e.g., in Apache/Nginx configuration) to reject unexpected values.

Long-Term Measures:

• Implement a Content Security Policy (CSP) to restrict redirect destinations.
• Conduct regular security audits of custom code and third-party integrations.
• Monitor for similar vulnerabilities in other routes.

Workaround (if patching is delayed):

• Disable the /legacy route if not needed, or restrict access via IP whitelisting.

Valters IT