CVE-2025-7320

Executive Summary

CVE-2025-7320 is a critical memory corruption vulnerability in the IrfanView CADImage Plugin when parsing DXF files. The flaw allows remote code execution (RCE) in the context of the current process, requiring user interaction (opening a malicious DXF file or visiting a malicious page). With a CVSS score of 7.8, this vulnerability poses a significant risk to users of IrfanView with the CADImage Plugin installed. No public exploit or patch is currently available, and the EPSS score is 0.0%, indicating low exploitation likelihood at this time.

CVSS Breakdown & Threat Level

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

Threat Level: High – Successful exploitation leads to full compromise of the affected system.

Deep Dive & Mechanics

The vulnerability resides in the CADImage Plugin’s DXF file parser. DXF (Drawing Exchange Format) is a CAD data file format developed by Autodesk. The plugin fails to properly validate user-supplied data during parsing, leading to a memory corruption condition. This corruption can be leveraged by an attacker to overwrite critical memory structures and achieve arbitrary code execution.

Root Cause: Lack of proper bounds checking or input validation when processing DXF file structures (e.g., entities, layers, or header sections). An attacker can craft a DXF file with malformed or oversized data fields to trigger a buffer overflow or use-after-free condition.

Attack Vector: Remote – The attacker delivers a malicious DXF file via email, download, or web page. The victim must open the file with IrfanView (with the CADImage Plugin installed).

Impact: Full system compromise under the privileges of the current user. This can lead to data theft, malware installation, or lateral movement within a network.

Vulnerable vs. Patched Code

Since no patch is available, a direct code comparison is not possible. However, the vulnerability is typical of memory corruption issues in C/C++ plugins. The vulnerable code likely lacks input validation:

Vulnerable (pseudo-code):

void parse_dxf_entity(char *data, int len) {
    char buffer[256];
    // No bounds check
    memcpy(buffer, data, len);
    // Process buffer...
}

Patched (expected):

void parse_dxf_entity(char *data, int len) {
    char buffer[256];
    if (len > sizeof(buffer)) {
        // Handle error
        return;
    }
    memcpy(buffer, data, len);
    // Process buffer...
}

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• IrfanView with CADImage Plugin installed (any version)
• A malicious DXF file crafted to trigger the memory corruption

Steps:

1. Craft a DXF file with an oversized or malformed entity section (e.g., a long string in the AcDbEntity layer name).
2. Deliver the file to the victim via phishing email or malicious website.
3. When the victim opens the file with IrfanView, the plugin parses the DXF and triggers the memory corruption.
4. The attacker’s shellcode executes in the context of IrfanView, granting code execution.

Example DXF structure (simplified):

0
SECTION
2
ENTITIES
0
LINE
8
[OVERFLOW_DATA_HERE]
10
0.0
20
0.0
11
1.0
21
1.0
0
ENDSEC
0
EOF

Note: No public exploit code is available. The above is a conceptual example.

Blue Team (Defense)

Detection:

• Monitor for unusual DXF files being opened by IrfanView.
• Use endpoint detection and response (EDR) to detect memory corruption events (e.g., access violations, crashes).
• Deploy YARA rules to scan for malicious DXF files.

Mitigation:

• Disable or uninstall the CADImage Plugin until a patch is released.
• Use application whitelisting to prevent IrfanView from executing untrusted plugins.
• Educate users not to open DXF files from untrusted sources.

Indicators of Compromise (IOCs)

• File Hashes: None available (no public samples)
• Network Indicators: None (exploitation is local)
• Behavioral Indicators:
  • IrfanView crash or access violation when opening a DXF file
  • Unexpected child processes spawned by IrfanView
  • Modification of memory regions associated with the CADImage Plugin

Detection Engineering

YARA Rule

rule CVE_2025_7320_DXF_Malicious {
    meta:
        description = "Detects malicious DXF files targeting CVE-2025-7320"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2025-7320"
    strings:
        $dxf_header = "0\nSECTION\n2\nENTITIES"
        $overflow = { 41 41 41 41 41 41 41 41 } // Example overflow pattern
    condition:
        $dxf_header and #overflow > 10
}

Sigma Rule

title: IrfanView CADImage Plugin DXF Memory Corruption
id: 8a9b3c4d-5e6f-7a8b-9c0d-1e2f3a4b5c6d
status: experimental
description: Detects potential exploitation of CVE-2025-7320 via DXF file parsing
author: Valters IT
date: 2025-04-10
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: 'i_view32.exe'
        CommandLine|contains: '.dxf'
    condition: selection
falsepositives:
    - Legitimate DXF file opening
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2025-7320 DXF File Download"; flow:to_client,established; file.name:"*.dxf"; content:"0|00|SECTION|00|2|00|ENTITIES"; distance:0; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. Disable the CADImage Plugin: Remove or rename the plugin DLL (e.g., CADImage.dll) in the IrfanView plugins directory.
2. User Education: Warn users not to open DXF files from untrusted sources.
3. Monitor for Exploitation: Deploy the provided detection rules.

Long-Term Fix:

• Await an official patch from IrfanView. Monitor the vendor’s website or ZDI advisory for updates.
• Consider using alternative image viewers that do not rely on the CADImage Plugin.

Workaround:

• Use a sandbox or virtual machine to open DXF files.
• Convert DXF files to a safer format (e.g., PDF) before viewing.

Valters IT