CVE-2025-0571

Executive Summary

CVE-2025-0571 is a memory corruption vulnerability in Sante PACS Server’s Web Portal, specifically during the parsing of DCM (DICOM) files. An authenticated remote attacker can trigger a denial-of-service (DoS) condition by sending a specially crafted DCM file. The flaw stems from improper validation of user-supplied data, leading to memory corruption. With a CVSS score of 6.5 (Medium), the vulnerability requires authentication but can cause system unavailability. No public exploit code or patch is currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
• Base Score: 6.5 (Medium)
• Attack Vector: Network
• Attack Complexity: Low
• Privileges Required: Low (authentication required)
• User Interaction: None
• Scope: Unchanged
• Confidentiality Impact: None
• Integrity Impact: None
• Availability Impact: High

The threat level is Medium due to the requirement for authentication, but the potential for a complete denial-of-service makes it significant for healthcare environments where PACS availability is critical.

Deep Dive & Mechanics

The vulnerability resides in the DCM file parsing component of the Sante PACS Server Web Portal. DCM files are standard medical imaging files (DICOM format). The parser fails to properly validate the size or structure of user-supplied data within the DCM file, leading to a memory corruption condition (likely a buffer overflow or out-of-bounds write). This corruption can cause the application to crash or become unresponsive, resulting in a denial-of-service.

Root Cause: Lack of bounds checking or input validation when processing DCM file fields, such as pixel data or metadata tags. An attacker can craft a DCM file with oversized or malformed fields to overwrite critical memory regions.

Attack Flow:

1. Attacker authenticates to the Sante PACS Web Portal (e.g., via valid credentials).
2. Attacker uploads or submits a malicious DCM file through the portal’s file upload or processing functionality.
3. The server parses the DCM file, triggering memory corruption.
4. The server process crashes or enters an infinite loop, causing a denial-of-service.

Vulnerable vs. Patched Code

Since no patch is available, a hypothetical vulnerable code snippet and a patched version are provided for illustration.

Vulnerable Code (C-style pseudocode):

void parse_dcm_file(char *data, size_t size) {
    char buffer[1024];
    // No bounds check on data copy
    memcpy(buffer, data, size);  // Potential overflow if size > 1024
    // Process buffer...
}

Patched Code:

void parse_dcm_file(char *data, size_t size) {
    char buffer[1024];
    if (size > sizeof(buffer)) {
        // Reject oversized data
        return;
    }
    memcpy(buffer, data, size);
    // Process buffer...
}

Exploitation & Lab Setup

Red Team

Prerequisites:

• Valid credentials for the Sante PACS Web Portal.
• Network access to the server (e.g., port 80/443).
• Ability to upload or submit DCM files.

Exploitation Steps:

1. Craft a malicious DCM file with an oversized pixel data field (e.g., set DICOM tag (7FE0,0010) to a size larger than the parser expects).
2. Authenticate to the web portal (e.g., via POST to /login).
3. Upload the malicious DCM file via the file upload endpoint (e.g., POST to /upload).
4. Monitor the server for crash or unresponsiveness.

Example Payload (Python):

import requests

url = "https://target-pacs-server/upload"
session = requests.Session()
session.post(url + "/login", data={"username": "user", "password": "pass"})

# Craft oversized DCM file (simplified)
malicious_dcm = b"\x00" * 10000  # Placeholder for real DCM structure
files = {"file": ("malicious.dcm", malicious_dcm)}
response = session.post(url, files=files)
print("Uploaded, check server status.")

Blue Team

Detection:

• Monitor for repeated crashes of the PACS server process.
• Look for DCM files with unusually large pixel data fields (e.g., > 100 MB).
• Alert on authentication followed by file uploads from the same IP within a short timeframe.

Mitigation:

• Restrict file upload sizes and validate DCM file structure server-side.
• Implement input sanitization and bounds checking in the parser.
• Use a Web Application Firewall (WAF) to block malformed DCM files.

Indicators of Compromise (IOCs)

• File Hashes: (None available; example)
  • malicious.dcm SHA256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
• Network Patterns:
  • POST requests to /upload with Content-Type: multipart/form-data containing DCM files.
  • Repeated HTTP 500 errors or connection resets after file upload.
• System Artifacts:
  • Crash dumps in /var/log/sante/ or Windows Event Logs (Application Error).
  • Memory corruption logs in application logs.

Detection Engineering

YARA Rule

rule CVE_2025_0571_Malicious_DCM {
    meta:
        description = "Detects potentially malicious DCM files targeting CVE-2025-0571"
        author = "Valters IT"
        date = "2025-02-20"
        reference = "CVE-2025-0571"
    strings:
        $dcm_header = "DICM" at 128
        $large_pixel = { (7F E0 00 10) }  // Pixel Data tag
    condition:
        $dcm_header and #large_pixel > 1 and filesize > 1000000
}

Sigma Rule

title: Sante PACS Server DoS via Malicious DCM Upload
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects upload of oversized DCM files to Sante PACS Web Portal
logsource:
    category: webserver
    product: apache
detection:
    selection:
        cs-method: 'POST'
        cs-uri-stem: '/upload'
        sc-status: 500
    condition: selection
falsepositives:
    - Legitimate large DCM files (rare)
level: high

Suricata Rule

alert http $HOME_NET any -> $EXTERNAL_NET any (
    msg:"CVE-2025-0571 Sante PACS DCM Upload DoS Attempt";
    flow:to_server,established;
    content:"POST"; http_method;
    content:"/upload"; http_uri;
    content:"multipart/form-data"; http_client_body;
    pcre:"/Content-Disposition: form-data; name=\"file\"; filename=\".*\.dcm\"/i";
    sid:1000001;
    rev:1;
)

Remediation & Mitigation

Immediate Actions:

• Disable the DCM file upload functionality if not essential.
• Implement strict input validation and size limits on DCM files (e.g., reject files > 50 MB).
• Apply memory safety mitigations (e.g., ASLR, DEP) on the server.

Long-term Fix:

• Await an official patch from Sante. Contact vendor for update status.
• Consider migrating to a different PACS solution if vendor does not patch.

Workaround:

• Use a reverse proxy to inspect and block malformed DCM files before they reach the server.

Valters IT