CVE-2024-7509

Executive Summary

CVE-2024-7509 is a critical stack-based buffer overflow vulnerability in Trimble SketchUp, a widely used 3D modeling application. The flaw resides in the parsing of SKP files, where insufficient validation of user-supplied data length leads to a stack-based buffer overflow. Successful exploitation requires user interaction (opening a malicious SKP file or visiting a malicious page), allowing remote attackers to execute arbitrary code in the context of the current process. The vulnerability was reported via the ZDI program (ZDI-CAN-19576) and currently has no known patch or public exploit. The CVSS score is 7.8 (High), and the EPSS probability is 0.0%, indicating low exploitation activity in the wild.

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a standalone desktop application (Trimble SketchUp). No supply chain package security implications are present.

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 (AV): Local (requires user to open a file or visit a page)
• Attack Complexity (AC): Low
• Privileges Required (PR): None
• User Interaction (UI): Required (victim must open malicious file)
• Scope (S): Unchanged
• Confidentiality (C): High
• Integrity (I): High
• Availability (A): High

Threat Level: High. Although no public exploit exists, the vulnerability is stack-based and can lead to full code execution. User interaction is required, but social engineering can easily trick users into opening malicious SKP files.

Deep Dive & Mechanics

The vulnerability is a classic stack-based buffer overflow (CWE-121) in Trimble SketchUp's SKP file parser. The SKP file format is proprietary and used for 3D models. The parser fails to validate the length of user-supplied data before copying it to a fixed-size stack buffer. An attacker can craft a malicious SKP file with an oversized field, causing a buffer overflow that overwrites the return address or other critical stack data.

Technical Details:

• Root Cause: Lack of bounds checking on a strcpy() or similar function when processing a specific field in the SKP file.
• Exploitation: By controlling the overflow data, an attacker can overwrite the saved return address on the stack, redirecting execution to attacker-controlled shellcode.
• Impact: Arbitrary code execution in the context of the SketchUp process, which may have user-level privileges.

Attack Vector:

1. Attacker crafts a malicious SKP file with a specially crafted field that exceeds the buffer size.
2. Attacker hosts the file on a website or sends it via email.
3. Victim opens the file in Trimble SketchUp.
4. The parser copies the oversized data into a stack buffer, overwriting the return address.
5. Upon function return, execution jumps to attacker-controlled shellcode.

Vulnerable vs. Patched Code

Since no patch is available, a hypothetical vulnerable code snippet is provided:

Vulnerable Code (C-like pseudocode):

void ParseSKPField(char *input) {
    char buffer[256];
    // No bounds checking
    strcpy(buffer, input);
    // Process buffer...
}

Patched Code (Hypothetical):

void ParseSKPField(char *input, size_t input_len) {
    char buffer[256];
    if (input_len >= sizeof(buffer)) {
        // Handle error
        return;
    }
    strncpy(buffer, input, sizeof(buffer) - 1);
    buffer[sizeof(buffer) - 1] = '\0';
    // Process buffer...
}

The patched version uses strncpy with proper length validation to prevent overflow.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Trimble SketchUp (vulnerable version, unknown)
• Python 3.x with struct module
• Metasploit or custom shellcode

Lab Setup:

1. Install a vulnerable version of Trimble SketchUp on a Windows VM.
2. Create a malicious SKP file using Python.

Exploit Script (Python):

import struct

# Shellcode (example: calc.exe)
shellcode = b"\x90" * 100  # Replace with actual shellcode

# Craft malicious SKP file
buffer_size = 256
overflow = b"A" * buffer_size + struct.pack("<I", 0x90909090) + shellcode

# Write to file
with open("malicious.skp", "wb") as f:
    f.write(overflow)

print("Malicious SKP file created: malicious.skp")

Usage:

1. Run the script to generate malicious.skp.
2. Send the file to the victim.
3. Victim opens the file in SketchUp.
4. Exploit triggers code execution.

Note: No public exploit exists; this is a conceptual example.

Blue Team (Defense)

Detection:

• Monitor for unusual SKP file sizes or anomalies.
• Use YARA rules to detect malicious SKP files.
• Enable ASLR and DEP on the system.

Mitigation:

• Block SKP files from untrusted sources.
• Use application whitelisting.
• Educate users about phishing attacks.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): Unknown (no known samples)
• Network Indicators: None (local file-based)
• Behavioral Indicators:
  • SketchUp process crash or unexpected termination.
  • Unusual child processes spawned by SketchUp (e.g., cmd.exe, powershell.exe).
  • High memory usage or stack corruption errors.

Detection Engineering

YARA Rule

rule CVE_2024_7509_SKP_Overflow {
    meta:
        description = "Detects malicious SKP files exploiting CVE-2024-7509"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "CVE-2024-7509"
    strings:
        $overflow = { 41 41 41 41 41 41 41 41 } // Pattern of 'A' characters
        $skp_magic = { 53 4B 50 } // "SKP" magic bytes
    condition:
        $skp_magic at 0 and #overflow > 10
}

Sigma Rule

title: CVE-2024-7509 - Trimble SketchUp SKP File Buffer Overflow
id: 12345678-1234-1234-1234-123456789012
status: experimental
description: Detects potential exploitation of CVE-2024-7509 via SKP file
author: Valters IT
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\SketchUp.exe'
        CommandLine|contains: '.skp'
    condition: selection
falsepositives:
    - Legitimate SKP files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-7509 - SKP File Download"; flow:to_server,established; content:"SKP"; nocase; fileext:"skp"; sid:1000001; rev:1;)

Remediation & Mitigation

Immediate Actions:

1. No patch available: Disable or restrict use of Trimble SketchUp until a patch is released.
2. User Education: Train users not to open SKP files from untrusted sources.
3. Application Control: Use AppLocker or similar to block SketchUp from executing untrusted scripts.

Long-term:

• Monitor vendor for patch updates.
• Implement file integrity monitoring for SKP files.
• Use sandboxing for file parsing.

Valters IT Signature:

---
Valters IT
Advanced Cyber Threat Intelligence
CVE-2024-7509 Analysis
Date: 2025-04-10
---