CVE-2024-9730

Executive Summary

CVE-2024-9730 is a critical memory corruption vulnerability in Trimble SketchUp Viewer, a widely used 3D modeling application. The flaw resides in the parsing of SKP files, where improper validation of user-supplied data can lead to memory corruption. An attacker can exploit this by convincing a user to open a malicious SKP file or visit a crafted web page, resulting in remote code execution (RCE) in the context of the current process. With a CVSS score of 7.8, this vulnerability poses a significant risk to end-user systems, particularly in design, engineering, and construction environments where SketchUp is prevalent. No public exploit code or patch is currently available, making user awareness and strict file handling policies the primary defense.

Supply Chain & Package Security

This vulnerability is not related to a package manager (NPM, PyPI, Go, Ruby) but is a desktop application issue. However, organizations using Trimble SketchUp Viewer should treat it as a critical supply chain risk, as malicious SKP files could be distributed via email, downloads, or shared project files.

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 (AV): Local – The attacker must have access to the system or trick the user into opening a file.
• Attack Complexity (AC): Low – No special conditions are required.
• Privileges Required (PR): None – No authentication needed.
• User Interaction (UI): Required – The victim must open the malicious file.
• Scope (S): Unchanged – The exploit affects only the vulnerable component.
• Confidentiality (C): High – Full data access possible.
• Integrity (I): High – Code execution allows modification.
• Availability (A): High – Potential for denial of service or system compromise.

Threat Level: High. The vulnerability is unpatched, and while no public exploit exists, the technical details (memory corruption in SKP parsing) are known, making it a prime target for targeted attacks.

Deep Dive & Mechanics

The vulnerability is a classic memory corruption issue in the SKP file parser of Trimble SketchUp Viewer. SKP files are binary format files containing 3D model data, including geometry, textures, and metadata. The parser fails to properly validate the size or structure of certain data fields, leading to a buffer overflow or use-after-free condition.

Technical Breakdown:

1. Entry Point: The vulnerability is triggered when SketchUp Viewer reads a specially crafted SKP file. This can occur via direct file open or through a web browser if the file is downloaded and automatically opened.
2. Root Cause: The parser does not enforce bounds checking on a specific data chunk (likely a string or array length field). An attacker can supply an oversized value, causing the parser to write beyond allocated memory.
3. Exploitation: By controlling the corrupted memory, an attacker can overwrite function pointers or return addresses, redirecting execution to shellcode embedded in the SKP file. The code runs with the privileges of the current user.
4. Impact: Full compromise of the user's system, including data theft, installation of malware, or lateral movement within a network.

Vulnerable vs. Patched Code

Since no patch is available, a direct comparison is not possible. However, based on the CWE-119 classification, the vulnerable code likely resembles:

Vulnerable (C-style pseudo-code):

void parse_skp_data(char *buffer, int size) {
    char name[256];
    int name_len = *(int*)buffer; // Attacker-controlled
    memcpy(name, buffer+4, name_len); // No bounds check
}

Patched (Hypothetical):

void parse_skp_data(char *buffer, int size) {
    char name[256];
    int name_len = *(int*)buffer;
    if (name_len > 255) { // Bounds check
        return error("Invalid name length");
    }
    memcpy(name, buffer+4, name_len);
}

The fix would involve adding validation for all user-supplied size fields before memory operations.

Exploitation & Lab Setup

Red Team (Exploitation)

No public exploit code is available. To develop a proof-of-concept:

1. Environment: Windows 10/11 with Trimble SketchUp Viewer (any version).
2. Tools: Python with struct module for binary crafting, a debugger (x64dbg), and a fuzzer (e.g., boofuzz).
3. Steps:
   • Fuzz the SKP file format to identify the crash point.
   • Analyze the crash in a debugger to determine overwritten registers.
   • Craft a malicious SKP file with shellcode (e.g., reverse shell).
   • Deliver via phishing email or malicious website.

Example Python script to generate a malformed SKP (conceptual):

import struct

# Craft a minimal SKP with oversized name length
skp_data = b'\x00' * 4  # Header
skp_data += struct.pack('<I', 0x1000)  # Malicious length
skp_data += b'A' * 0x1000  # Overflow data

with open('malicious.skp', 'wb') as f:
    f.write(skp_data)

Blue Team (Defense)

• Detection: Monitor for unusual SKP file downloads or execution of SketchUp Viewer with high memory usage.
• Prevention: Use application whitelisting to block SketchUp Viewer if not required. Enable Attack Surface Reduction (ASR) rules to block Office apps from creating child processes.
• Hunting: Search for processes named SketchUp.exe or SketchUpViewer.exe with abnormal crash logs.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): No known malicious samples yet.
• Network: Outbound connections from SketchUp Viewer to unknown IPs (potential reverse shell).
• Process: SketchUp.exe or SketchUpViewer.exe crashing repeatedly.
• Registry: Unusual entries under HKCU\Software\Trimble\SketchUp.
• File System: Presence of .skp files in unusual locations (e.g., %TEMP%).

Detection Engineering

YARA Rule

rule CVE_2024_9730_SKP_Malicious {
    meta:
        description = "Detects malicious SKP files exploiting CVE-2024-9730"
        author = "Valters IT"
        date = "2025-04-10"
        hash = "unknown"
    strings:
        $skp_header = { 00 00 00 00 }  // Example SKP magic bytes
        $overflow = { FF FF FF FF }    // Potential oversized length
    condition:
        $skp_header at 0 and $overflow
}

Sigma Rule

title: Suspicious SketchUp Viewer Execution with Crash
id: 7b8c9d0e-1f2a-3b4c-5d6e-7f8a9b0c1d2e
status: experimental
description: Detects potential exploitation of CVE-2024-9730 via SketchUp Viewer crashes
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\SketchUp.exe'
        CommandLine|contains: '.skp'
    condition: selection
falsepositives:
    - Legitimate use of SketchUp Viewer
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-9730 Potential SKP Exploit Outbound"; flow:to_server,established; content:"|00 00 00 00|"; depth:4; content:"|FF FF FF FF|"; within:100; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

1. Immediate Actions:

   • Disable automatic opening of SKP files in web browsers.
   • Educate users to not open SKP files from untrusted sources.
   • Use a sandbox or virtual machine for viewing untrusted SKP files.

2. Long-term:

   • Monitor Trimble’s advisory page for a patch.
   • Implement application control to restrict SketchUp Viewer execution.
   • Deploy endpoint detection and response (EDR) with behavioral analytics.

3. Workarounds:

   • Convert SKP files to a safer format (e.g., STL) before opening.
   • Use a dedicated file scanner for SKP files.

Valters IT Signature This report was generated by Valters IT DevSecOps AI. For questions, contact security@valters-it.com.