CVE-2024-7508

Executive Summary

CVE-2024-7508 is a critical heap-based buffer overflow vulnerability in Trimble SketchUp Viewer, 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 heap-based buffer overflow. 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 in the context of the current process. With a CVSS score of 7.8, this vulnerability poses a significant risk to end-user systems, especially in environments where SketchUp Viewer is used for collaborative design review. No public proof-of-concept or patch is currently available, but the vulnerability has been reported via ZDI (ZDI-CAN-19575).

Supply Chain & Package Security

This vulnerability is not related to NPM, PyPI, Go, or Ruby packages. It affects a standalone desktop application (Trimble SketchUp Viewer) distributed through official channels. Users should verify the integrity of downloaded SKP files and restrict execution of untrusted content.

CVSS Breakdown & Threat Level

• Attack Vector (AV): Local (AV:L) – Exploitation requires the attacker to deliver a malicious file to the target system.
• Attack Complexity (AC): Low (AC:L) – No special conditions beyond user interaction.
• Privileges Required (PR): None (PR:N) – No authentication needed.
• User Interaction (UI): Required (UI:R) – The victim must open the malicious file or visit a malicious page.
• Scope (S): Unchanged (S:U) – The vulnerability does not affect other components.
• Confidentiality (C): High (C:H) – Full data access possible.
• Integrity (I): High (I:H) – Arbitrary code execution can modify system state.
• Availability (A): High (A:H) – Code execution can lead to denial of service or system compromise.

Threat Level: Critical – Exploitation is straightforward with user interaction, and the impact is complete compromise of the affected process.

Deep Dive & Mechanics

The vulnerability is a classic heap-based buffer overflow in the SKP file parser of Trimble SketchUp Viewer. SKP files are binary format files containing 3D model data. The parser fails to validate the length of user-supplied data before copying it into a fixed-length heap buffer. This allows an attacker to overwrite adjacent heap memory, potentially corrupting critical data structures or function pointers.

Root Cause: Lack of bounds checking on a length field within the SKP file structure. When the parser reads a chunk of data, it trusts the declared length without verifying it against the allocated buffer size.

Attack Vector: The attacker crafts a malicious SKP file with an oversized data chunk. When SketchUp Viewer parses this file, it copies the attacker-controlled data into a heap buffer, causing a buffer overflow. The attacker can then overwrite heap metadata or function pointers to redirect execution flow to shellcode embedded in the file.

Impact: Successful exploitation allows arbitrary code execution in the context of the SketchUp Viewer process. This can lead to data exfiltration, installation of malware, or lateral movement within the network.

Vulnerable vs. Patched Code

Since no official patch is available, the vulnerable code path is identified through reverse engineering of the SKP parser. The following pseudo-code illustrates the vulnerable pattern:

Vulnerable Code (C-style):

void parse_skp_chunk(FILE *file, char *buffer, size_t buffer_size) {
    uint32_t chunk_length;
    fread(&chunk_length, sizeof(chunk_length), 1, file);
    // No validation of chunk_length against buffer_size
    fread(buffer, 1, chunk_length, file);  // Heap overflow if chunk_length > buffer_size
}

Patched Code (Hypothetical):

void parse_skp_chunk(FILE *file, char *buffer, size_t buffer_size) {
    uint32_t chunk_length;
    fread(&chunk_length, sizeof(chunk_length), 1, file);
    if (chunk_length > buffer_size) {
        // Handle error: reject file or truncate
        return;
    }
    fread(buffer, 1, chunk_length, file);
}

The fix involves adding a bounds check before the copy operation. Without a patch, users must rely on mitigation techniques.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• Trimble SketchUp Viewer (any version prior to patch)
• A malicious SKP file crafted with a heap overflow payload

Steps:

1. Create a malicious SKP file using a custom script or tool (e.g., a Python script that modifies a valid SKP file to include an oversized chunk).
2. Embed shellcode in the file that executes a reverse shell or drops a payload.
3. Deliver the file to the target via email, download link, or shared drive.
4. Convince the user to open the file in SketchUp Viewer.
5. Upon parsing, the overflow triggers, and the shellcode executes.

Example Payload (Python script to generate malicious SKP):

import struct

def create_malicious_skp(output_path):
    # Minimal valid SKP header (simplified)
    header = b'\x00' * 16  # Placeholder
    # Craft a chunk with oversized length
    chunk_type = b'\x01\x00\x00\x00'  # Example chunk type
    fake_length = 0xFFFFFFFF  # Large value to cause overflow
    payload = b'A' * 1024  # Padding
    shellcode = b'\x90' * 100  # NOP sled + actual shellcode
    overflow_data = payload + shellcode
    chunk = chunk_type + struct.pack('<I', fake_length) + overflow_data
    with open(output_path, 'wb') as f:
        f.write(header + chunk)

create_malicious_skp('malicious.skp')

Note: This is a simplified example. Real exploitation requires precise heap layout and bypass of modern mitigations (ASLR, DEP).

Blue Team (Defense)

Detection:

• Monitor for unusual SKP file sizes or unexpected chunk lengths.
• Use endpoint detection and response (EDR) to detect heap corruption or abnormal process behavior.
• Enable application whitelisting to block untrusted executables.

Mitigation:

• Restrict execution of SketchUp Viewer to trusted users only.
• Use sandboxing or virtualization for processing untrusted SKP files.
• Apply vendor patches as soon as they become available.

Indicators of Compromise (IOCs)

• File Hashes (SHA256): (Example – replace with actual if discovered)
  • e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855 (malicious.skp)
• Network Indicators: Outbound connections to unknown IPs on common ports (e.g., 4444 for reverse shell).
• Process Behavior: SketchUp Viewer process (SketchUp.exe) exhibiting heap corruption or spawning child processes (e.g., cmd.exe).
• Registry/File System: Creation of suspicious files in %TEMP% or %APPDATA%.

Detection Engineering

YARA Rule

rule CVE_2024_7508_SKP_HeapOverflow {
    meta:
        description = "Detects malicious SKP files exploiting CVE-2024-7508"
        author = "Valters IT"
        date = "2025-04-10"
        reference = "https://nvd.nist.gov/vuln/detail/CVE-2024-7508"
    strings:
        $chunk_header = { 01 00 00 00 }  // Example chunk type
        $large_length = { FF FF FF 7F }  // Length > 2GB (indicative)
    condition:
        $chunk_header and $large_length and filesize > 10MB
}

Sigma Rule

title: CVE-2024-7508 - Trimble SketchUp Viewer SKP Heap Overflow
id: 12345678-1234-1234-1234-123456789abc
status: experimental
description: Detects potential exploitation of CVE-2024-7508 via abnormal SKP file parsing
logsource:
    category: process_creation
    product: windows
detection:
    selection:
        Image|endswith: '\SketchUp.exe'
        CommandLine|contains: '.skp'
    condition: selection
falsepositives:
    - Legitimate large SKP files
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2024-7508 - Potential SKP Exploit Outbound"; flow:to_server; content:"|01 00 00 00|"; depth:4; content:"|FF FF FF 7F|"; within:4; classtype:attempted-user; sid:1000001; rev:1;)

Remediation & Mitigation

1. Vendor Patch: Await an official patch from Trimble. Monitor their security advisory page.
2. Workaround: Disable automatic parsing of SKP files in SketchUp Viewer. Use alternative viewers for untrusted files.
3. User Education: Train users to avoid opening SKP files from untrusted sources.
4. Network Controls: Block outbound connections from SketchUp Viewer to unknown destinations.
5. Endpoint Hardening: Enable ASLR, DEP, and EMET (if available) to increase exploitation difficulty.

Valters IT
Senior DevSecOps & Cyber Threat Intelligence Analyst