CVE-2025-2757: Assimp Buffer Overflow Vulnerability

CVE-2025-2757 Overview

A critical heap-based buffer overflow vulnerability has been identified in Open Asset Import Library (Assimp) version 5.4.3. This vulnerability exists within the AI_MD5_PARSE_STRING_IN_QUOTATION function located in the code/AssetLib/MD5/MD5Parser.cpp file, which is part of the MD5 File Handler component. The flaw allows remote attackers to exploit improper memory handling when processing specially crafted MD5 files, potentially leading to memory corruption, application crashes, or arbitrary code execution.

Critical Impact

Remote attackers can exploit this heap-based buffer overflow by supplying malicious MD5 files to applications using the vulnerable Assimp library, potentially compromising system integrity and confidentiality.

Affected Products

• Open Asset Import Library (Assimp) version 5.4.3
• Applications and game engines integrating Assimp for 3D asset importing
• Development environments utilizing Assimp for MD5 model file processing

Discovery Timeline

• 2025-03-25 - CVE-2025-2757 published to NVD
• 2025-07-17 - Last updated in NVD database

Technical Details for CVE-2025-2757

Vulnerability Analysis

This vulnerability is classified as a heap-based buffer overflow (CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer). The flaw resides in the MD5 file parsing functionality of Assimp, specifically within the string parsing routine that handles quoted strings in MD5 model files.

When the AI_MD5_PARSE_STRING_IN_QUOTATION function processes the data argument from a malformed MD5 file, it fails to properly validate the boundaries of input data before copying content to heap-allocated memory. This allows an attacker to craft a malicious MD5 file that causes the parser to write beyond the allocated buffer boundaries, corrupting adjacent heap memory structures.

The attack can be initiated remotely, as the vulnerability is exploitable through network-delivered MD5 files. An attacker could distribute malicious 3D model files through various channels including game asset downloads, 3D model sharing platforms, or embedded in other content delivery mechanisms.

Root Cause

The root cause of this vulnerability stems from insufficient bounds checking in the AI_MD5_PARSE_STRING_IN_QUOTATION macro or function when parsing string data enclosed in quotation marks within MD5 files. The parser does not adequately validate the length of string content before writing to the destination buffer, allowing oversized input to overflow the allocated heap memory region.

The MD5 file format, commonly used for animated 3D models, contains mesh and animation data that includes various string parameters. The vulnerable code path is triggered when these string parameters exceed expected boundaries, and the parser continues writing past the allocated buffer.

Attack Vector

The attack vector for CVE-2025-2757 is network-based, requiring user interaction to open or process a malicious MD5 file. An attacker could exploit this vulnerability through the following scenarios:

The vulnerability can be triggered when a user opens a maliciously crafted MD5 file using any application that utilizes the Assimp library for 3D asset importing. This includes game engines, 3D modeling software, asset converters, and various development tools. The exploit has been publicly disclosed, increasing the risk of exploitation in the wild.

Technical details regarding the vulnerability can be found in the GitHub Issue #6019 which documents the vulnerability disclosure. Additional information is available through VulDB #300862.

Detection Methods for CVE-2025-2757

Indicators of Compromise

• Unexpected application crashes when processing MD5 model files
• Memory access violations or segmentation faults in applications using Assimp
• Abnormal heap memory consumption patterns during 3D asset import operations
• Presence of unusually large or malformed MD5 files in asset directories

Detection Strategies

• Implement file integrity monitoring for directories containing 3D asset files
• Deploy endpoint detection solutions capable of identifying heap overflow exploitation attempts
• Monitor application logs for crashes related to MD5 file parsing or Assimp library operations
• Utilize memory protection mechanisms such as ASLR, DEP, and heap guards to detect exploitation attempts

Monitoring Recommendations

• Enable crash dump collection and analysis for applications utilizing Assimp
• Implement file type validation and sanitization for all incoming 3D model files
• Monitor for suspicious network transfers of MD5 files from untrusted sources
• Configure application whitelisting to restrict MD5 file processing to trusted asset sources

How to Mitigate CVE-2025-2757

Immediate Actions Required

• Audit all applications in your environment that depend on Assimp library version 5.4.3
• Implement input validation to reject MD5 files from untrusted sources pending patch availability
• Consider disabling MD5 file format support if not critical to operations
• Apply network-level filtering to block potentially malicious 3D model file transfers

Patch Information

As of the last NVD update on 2025-07-17, organizations should monitor the Assimp GitHub repository for official patches and security updates. It is recommended to upgrade to patched versions of Assimp as soon as they become available from the vendor.

Workarounds

• Restrict MD5 file processing to files from verified and trusted sources only
• Implement application sandboxing to contain potential exploitation impact
• Use memory-safe compilation options such as stack canaries and address sanitization during development
• Deploy runtime application self-protection (RASP) solutions to detect and block exploitation attempts

# Configuration example - Compile applications with memory protection flags
# Enable Address Sanitizer during development builds
export CFLAGS="-fsanitize=address -fno-omit-frame-pointer"
export CXXFLAGS="-fsanitize=address -fno-omit-frame-pointer"

# Recompile applications using Assimp with hardened options
cmake -DCMAKE_BUILD_TYPE=RelWithDebInfo \
      -DCMAKE_C_FLAGS="-D_FORTIFY_SOURCE=2 -fstack-protector-strong" \
      -DCMAKE_CXX_FLAGS="-D_FORTIFY_SOURCE=2 -fstack-protector-strong" \
      ..