CVE-2023-32134

Executive Summary

CVE-2023-32134 is a critical use-after-free vulnerability in Sante DICOM Viewer Pro, specifically during the parsing of DCM image files. The flaw allows remote code execution (RCE) in the context of the current process, requiring user interaction (e.g., opening a malicious DCM file or visiting a crafted page). With a CVSS score of 7.8, this vulnerability poses a high risk to medical imaging workflows and healthcare environments. No public proof-of-concept (PoC) or patch is currently available, and the EPSS score is 0.0%, indicating low exploitation activity. However, the lack of a patch and the sensitive nature of DICOM data make this a significant threat for targeted attacks.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a standalone desktop application (Sante DICOM Viewer Pro) used in medical imaging. Supply chain risks are limited to the distribution of the application itself.

CVSS Breakdown & Threat Level

• CVSS Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
• Base Score: 7.8 (High)
• Attack Vector: Local (requires user to open a malicious file)
• Attack Complexity: Low
• Privileges Required: None
• User Interaction: Required
• Scope: Unchanged
• Confidentiality Impact: High
• Integrity Impact: High
• Availability Impact: High

Threat Level: High. Although no active exploitation is reported, the vulnerability allows full compromise of the application and system, making it attractive for targeted attacks against healthcare organizations.

Deep Dive & Mechanics

The vulnerability resides in the DCM image parsing module of Sante DICOM Viewer Pro. A use-after-free condition occurs when the application fails to validate the existence of an object before performing operations on it. Specifically, during the parsing of a crafted DCM file, an object is freed but a pointer to it remains, allowing an attacker to control the freed memory. This can be leveraged to execute arbitrary code.

Root Cause: Lack of proper validation of object lifetime in the DCM parsing routine. The code does not check if a referenced object is still valid after certain operations, leading to a dangling pointer.

Attack Vector: Remote, but requires user interaction. An attacker can host a malicious DCM file on a website or send it via email. When the user opens the file with Sante DICOM Viewer Pro, the vulnerability is triggered.

Impact: Successful exploitation allows the attacker to execute arbitrary code in the context of the current process, potentially leading to full system compromise, data exfiltration, or ransomware deployment.

Vulnerable vs. Patched Code

No official patch is available. The vulnerable code is in the DCM parsing function, likely in a library such as dcmtk or a custom parser. A hypothetical fix would involve adding a check for object validity before use:

Vulnerable Code (Pseudocode):

void parse_dcm_image(DCM_Image *img) {
    Object *obj = get_object_from_image(img);
    // ... some operations that may free obj ...
    process_object(obj);  // Use-after-free if obj was freed
}

Patched Code (Hypothetical):

void parse_dcm_image(DCM_Image *img) {
    Object *obj = get_object_from_image(img);
    // ... some operations that may free obj ...
    if (obj != NULL && is_object_valid(obj)) {
        process_object(obj);
    } else {
        // Handle error
    }
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Sante DICOM Viewer Pro (any version)
• A crafted DCM file with a use-after-free trigger

Steps:

1. Create a malicious DCM file using a fuzzer or manual crafting to trigger the use-after-free.
2. Host the file on a web server or send it via email.
3. Convince the target to open the file (e.g., via social engineering).
4. Upon opening, the exploit executes arbitrary code in the context of the viewer.

No public exploit code is available. The following is a conceptual example of a DCM file structure that could trigger the vulnerability:

# Conceptual exploit generator (not functional)
import struct

def create_malicious_dcm():
    # Craft a DCM file with malformed tags to trigger use-after-free
    # This is a placeholder; actual exploitation requires deep knowledge of the parser
    dcm_data = b'\x00' * 1000  # Placeholder
    with open('malicious.dcm', 'wb') as f:
        f.write(dcm_data)

create_malicious_dcm()

Blue Team (Defense)

Detection:

• Monitor for unusual DCM file downloads or email attachments.
• Use endpoint detection and response (EDR) to detect abnormal process behavior (e.g., memory corruption, code injection).
• Implement application whitelisting to prevent unauthorized executables.

Mitigation:

• Restrict user permissions to run Sante DICOM Viewer Pro.
• Use sandboxing or virtualization for processing untrusted DCM files.
• Educate users about the risks of opening DCM files from untrusted sources.

Indicators of Compromise (IOCs)

• File Hashes: No known malicious files yet.
• Network Indicators: Connections to unknown IPs after exploitation (e.g., C2 servers).
• Process Indicators: Sante DICOM Viewer Pro crashing or exhibiting abnormal memory usage.
• Registry/File System: Creation of suspicious files in temporary directories.

Example IOC:

iocs:
  - type: file
    description: Malicious DCM file
    hash: UNKNOWN
  - type: network
    description: C2 communication
    ip: UNKNOWN
    port: UNKNOWN

Detection Engineering

YARA Rule

rule CVE_2023_32134_Sante_DICOM_UseAfterFree {
    meta:
        description = "Detects malicious DCM files targeting CVE-2023-32134"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2023-32134"
    strings:
        $dcm_header = "DICM"  // DICOM file header
        $suspicious_tag = { (?? ?? ?? ?? 00 00 00 00) }  // Placeholder for malformed tag
    condition:
        $dcm_header at 128 and #suspicious_tag > 0
}

Sigma Rule

title: Sante DICOM Viewer Pro Use-After-Free Exploitation Attempt
id: 8a4b3c2d-1e5f-6a7b-8c9d-0e1f2a3b4c5d
status: experimental
description: Detects potential exploitation of CVE-2023-32134 via abnormal process behavior
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: 'SanteDicomViewerPro.exe'
        CommandLine|contains: '.dcm'
    condition: selection
falsepositives:
    - Legitimate DCM file processing
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2023-32134 Sante DICOM Viewer Pro Exploit Attempt"; flow:to_server,established; content:"DICM"; offset:128; depth:4; content:"|00 00 00 00|"; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

• Disable or restrict the use of Sante DICOM Viewer Pro until a patch is available.
• Use alternative DICOM viewers that are actively maintained.
• Implement strict file upload/download policies to block untrusted DCM files.

Long-Term:

• Monitor vendor channels for a security update.
• Consider using a DICOM proxy or sandbox to inspect files before opening.
• Conduct regular security audits of medical imaging software.

Workarounds:

• Enable Windows Defender Exploit Guard or similar mitigations.
• Use application control policies to prevent execution of untrusted code.

Valters IT
Securing Digital Frontiers