CVE-2025-2750: Assimp Buffer Overflow Vulnerability

CVE-2025-2750 Overview

A critical out-of-bounds write vulnerability has been identified in the Open Asset Import Library (Assimp) version 5.4.3. This vulnerability exists within the Assimp::CSMImporter::InternReadFile function located in the code/AssetLib/CSM/CSMLoader.cpp file of the CSM File Handler component. When processing specially crafted CSM files, the application fails to properly validate input boundaries, resulting in memory corruption that can be exploited remotely.

Critical Impact

Remote attackers can trigger an out-of-bounds write condition by supplying a malicious CSM file, potentially leading to application crashes, data corruption, or arbitrary code execution in applications that use the Assimp library for 3D model import functionality.

Affected Products

• Open Asset Import Library (Assimp) version 5.4.3
• Applications and game engines using Assimp 5.4.3 for 3D asset importing
• Development tools and pipelines incorporating the vulnerable Assimp library

Discovery Timeline

• 2025-03-25 - CVE-2025-2750 published to NVD
• 2025-07-17 - Last updated in NVD database

Technical Details for CVE-2025-2750

Vulnerability Analysis

The vulnerability resides in the CSM (Character Studio Motion) file parser within the Assimp library. The Assimp::CSMImporter::InternReadFile function processes CSM motion capture files but fails to implement adequate boundary checks when writing parsed data to memory buffers. This memory safety issue falls under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).

When parsing malformed or maliciously crafted CSM files, the function can write data beyond the allocated buffer boundaries. This out-of-bounds write condition corrupts adjacent memory regions, which attackers could potentially leverage to manipulate program execution flow or cause denial of service conditions.

The vulnerability is remotely exploitable as users can be tricked into opening malicious CSM files through applications that integrate the Assimp library for 3D model and motion data import. The exploit has been publicly disclosed, increasing the risk of active exploitation attempts.

Root Cause

The root cause of this vulnerability is insufficient input validation in the CSM file parsing logic. The InternReadFile function in CSMLoader.cpp does not properly verify the size and boundaries of data elements within CSM files before writing them to internal buffers. When processing files with unexpected or malicious size values, the parser continues writing beyond allocated memory regions, resulting in an out-of-bounds write condition.

Attack Vector

The attack vector is network-based, requiring user interaction. An attacker can exploit this vulnerability through the following scenario:

1. The attacker crafts a malicious CSM file containing manipulated header values or data elements designed to trigger the buffer overflow
2. The malicious file is distributed through various channels (email attachments, download links, game modding communities, 3D asset repositories)
3. When a victim opens the malicious CSM file using any application that integrates Assimp 5.4.3 for 3D asset processing, the vulnerability is triggered
4. The out-of-bounds write corrupts memory, potentially allowing code execution or causing application crash

The vulnerability mechanism involves the CSM parser reading size or count values from the file header without proper validation, then using these values to determine write operations to memory buffers. By providing crafted values that exceed expected bounds, an attacker can force writes beyond the allocated buffer space. For detailed technical analysis, refer to the GitHub Issue Discussion.

Detection Methods for CVE-2025-2750

Indicators of Compromise

• Unexpected application crashes when processing CSM or 3D model files
• Memory access violation errors in applications using Assimp library
• Suspicious CSM files with abnormal file sizes or malformed headers
• Application crashes specifically triggered by CSM file imports in 3D tools or game engines

Detection Strategies

• Monitor applications using Assimp for abnormal crash patterns during file import operations
• Implement file validation checks for CSM files before processing with the Assimp library
• Deploy endpoint detection and response (EDR) solutions to detect memory corruption exploitation attempts
• Use application whitelisting to prevent execution of unauthorized binaries resulting from potential exploitation

Monitoring Recommendations

• Enable crash dump collection for applications using Assimp to analyze exploitation attempts
• Monitor network traffic for suspicious downloads of CSM files from untrusted sources
• Implement logging for all 3D asset import operations in production environments
• Set up alerts for repeated application crashes in systems processing 3D model files

How to Mitigate CVE-2025-2750

Immediate Actions Required

• Audit all applications and development pipelines to identify usage of Assimp version 5.4.3
• Restrict processing of CSM files from untrusted sources until a patch is applied
• Implement input sanitization and file validation before processing CSM files with Assimp
• Consider disabling CSM file import functionality if not required for your application
• Monitor the Assimp GitHub repository for official patches and updates

Patch Information

As of the last NVD update on 2025-07-17, organizations should monitor the official Assimp GitHub repository for security patches addressing this vulnerability. Check the Assimp GitHub Issues for the latest status on fixes. When a patch becomes available, test and deploy it to all affected systems promptly.

Workarounds

• Disable CSM file format support in Assimp if not required for your application's functionality
• Implement strict file validation to reject CSM files that exceed expected size thresholds
• Process untrusted 3D files in sandboxed environments to contain potential exploitation
• Use allow-listing to only permit CSM files from trusted, verified sources
• Consider alternative libraries for CSM parsing until the vulnerability is patched

# Configuration example: Disable CSM importer at compile time
# When building Assimp from source, disable the CSM importer
cmake -DASSIMP_BUILD_CSM_IMPORTER=OFF ..

# Alternatively, remove CSM files before processing
find /path/to/assets -name "*.csm" -type f -delete