CVE-2025-2756: Assimp Heap Buffer Overflow Vulnerability

CVE-2025-2756 Overview

CVE-2025-2756 is a heap-based buffer overflow vulnerability in Open Asset Import Library (Assimp) version 5.4.3. The flaw resides in the Assimp::AC3DImporter::ConvertObjectSection function within code/AssetLib/AC/ACLoader.cpp, part of the AC3D File Handler component. Manipulation of the tmp argument triggers the overflow on the heap. The vulnerability is categorized under [CWE-119] for improper restriction of operations within memory bounds. An attacker can deliver a crafted AC3D file to a vulnerable application that parses it through Assimp, initiating the attack remotely. The exploit has been publicly disclosed, increasing the risk that attackers will weaponize it against software that embeds the library.

Critical Impact
A remote attacker can deliver a malicious AC3D file that corrupts heap memory in any application using Assimp 5.4.3, potentially enabling code execution or process crashes.

Affected Products

Open Asset Import Library (Assimp) 5.4.3
Applications embedding Assimp 5.4.3 for 3D asset loading
AC3D File Handler component (code/AssetLib/AC/ACLoader.cpp)

Discovery Timeline

2025-03-25 - CVE-2025-2756 published to NVD
2025-07-17 - Last updated in NVD database

Technical Details for CVE-2025-2756

Vulnerability Analysis

Assimp is a widely used open-source library for importing and processing 3D model formats. CVE-2025-2756 affects the AC3D format importer, specifically the ConvertObjectSection function in ACLoader.cpp. The function processes object section data from AC3D files and writes intermediate results into a buffer referenced by the tmp argument. When attacker-controlled input drives the size or content of tmp beyond the allocated heap region, the library writes past the buffer boundary. This corrupts adjacent heap metadata or object data, producing memory corruption that an attacker can use to influence program execution or crash the host process.

Root Cause

The root cause is missing or insufficient bounds validation when populating the tmp argument inside ConvertObjectSection. The importer trusts size or count values derived from the input AC3D file without verifying them against the allocated buffer size. This pattern aligns with [CWE-119], improper restriction of operations within the bounds of a memory buffer, and is typical for parsers that accept attacker-supplied structured input.

Attack Vector

Exploitation requires the victim to load a crafted AC3D file through an application that uses Assimp 5.4.3. Attack delivery can occur over the network through file downloads, email attachments, web-based 3D viewers, game asset pipelines, or document workflows that ingest 3D content. No authentication is required, but the user must open or otherwise process the malicious file. Once parsed, the heap-based buffer overflow corrupts memory, enabling denial of service and, depending on heap layout and process mitigations, possible code execution. Public disclosure on the Assimp GitHub Issue Tracker and VulDB entry #300861 makes the affected code path documented and reproducible.

No verified proof-of-concept code is published in the enriched data set, so technical details are described in prose. See the GitHub issue discussion for additional context.

Detection Methods for CVE-2025-2756

Indicators of Compromise

Unexpected crashes or abnormal terminations in processes that load AC3D (.ac) files through Assimp
Heap corruption signatures in crash dumps referencing ConvertObjectSection or ACLoader.cpp
Inbound AC3D files from untrusted sources delivered through email, web downloads, or asset repositories

Detection Strategies

Inventory applications and dependencies that bundle Assimp and confirm the linked version against 5.4.3
Enable Address Sanitizer (ASan) or equivalent heap instrumentation in development and QA pipelines that parse AC3D files
Apply file-type inspection at email and web gateways to flag AC3D content originating from external sources

Monitoring Recommendations

Collect and review crash telemetry from endpoints running 3D modeling, gaming, CAD, or rendering software for faults in Assimp modules
Log file-open events for .ac extensions and correlate with process exceptions in endpoint detection telemetry
Track software bill of materials (SBOM) data to identify products that statically link or bundle vulnerable Assimp builds

How to Mitigate CVE-2025-2756

Immediate Actions Required

Identify every internal and third-party application that embeds Assimp 5.4.3 and prioritize patching for those handling untrusted AC3D files
Block ingestion of .ac files from untrusted external sources at email and web gateways until affected components are updated
Restrict permissions on processes that parse 3D assets so heap corruption cannot escalate beyond the user context

Patch Information

No vendor patch link is listed in the enriched advisory data at the time of writing. Monitor the Assimp GitHub repository for fix commits to code/AssetLib/AC/ACLoader.cpp and upgrade to a release that addresses the ConvertObjectSection bounds check. Rebuild and redeploy any downstream applications that statically link Assimp once a fixed version is published.

Workarounds

Disable the AC3D importer in Assimp build configurations where the format is not required
Sandbox processes that parse untrusted 3D files using OS-level isolation such as AppContainer, seccomp, or container runtimes
Validate file provenance and apply allow-lists for 3D asset sources in production pipelines

bash

# Configuration example: rebuild Assimp with AC3D importer disabled
cmake -DASSIMP_BUILD_AC_IMPORTER=OFF -DASSIMP_BUILD_TESTS=OFF ..
make -j$(nproc)
sudo make install