CVE-2026-10233: Assimp Buffer Overflow Vulnerability

CVE-2026-10233 Overview

CVE-2026-10233 is an out-of-bounds read vulnerability in the Open Asset Import Library (Assimp) through version 6.0.4. The flaw resides in the HL1MDLLoader::read_sequence_infos function inside HL1MDLLoader.cpp, part of the Half-Life 1 MDL Loader component. Manipulation of the aiString argument triggers a read past allocated buffer boundaries [CWE-119]. The issue requires local access and low privileges to exploit. A public proof-of-concept has been disclosed, and the Assimp project has classified the report as a bug.

Critical Impact
An attacker with local access can supply a crafted Half-Life 1 MDL model file to trigger an out-of-bounds read, potentially leaking process memory or crashing applications that use Assimp for 3D asset import.

Affected Products

Assimp (Open Asset Import Library) versions up to and including 6.0.4
Applications embedding the vulnerable HL1MDLLoader component
3D content pipelines and tools that parse Half-Life 1 MDL files via Assimp

Discovery Timeline

2026-06-01 - CVE-2026-10233 published to NVD
2026-06-03 - Last updated in NVD database

Technical Details for CVE-2026-10233

Vulnerability Analysis

The vulnerability lives in Assimp's parser for Half-Life 1 model (MDL) files. During sequence information parsing, HL1MDLLoader::read_sequence_infos reads bytes from the input file into an aiString structure without correctly validating the size or termination of the source data. The parser walks past the boundary of the allocated buffer and reads adjacent memory.

Assimp is widely embedded in game engines, 3D modeling tools, and asset pipelines, which expands the attack surface to any application that imports untrusted model files. The Assimp maintainers have tagged the issue as a bug in the project tracker. EPSS data places the probability of exploitation in the wild at very low levels, consistent with the local attack vector and limited impact scope.

Root Cause

The root cause is missing bounds enforcement when populating an aiString from MDL sequence data. The loader trusts size fields or string terminators present in the file rather than constraining reads to the actual buffer length. When a malformed MDL file contains an oversized or unterminated string field, the read operation overruns the source buffer.

Attack Vector

Exploitation requires the attacker to deliver a crafted .mdl file to a target that uses Assimp 6.0.4 or earlier. The attack vector is local: a user must open or import the malicious file in an application that invokes the Half-Life 1 MDL loader. Successful exploitation produces an out-of-bounds read that can disclose process memory, corrupt parser state, or cause the host application to crash.

No verified exploitation code is reproduced here. A public proof-of-concept archive is referenced from the GitHub Issue #6619 tracking this report.

Detection Methods for CVE-2026-10233

Indicators of Compromise

Application crashes or abnormal terminations in processes that load .mdl files through Assimp
Unexpected memory access violations originating from HL1MDLLoader.cpp stack frames
Presence of untrusted Half-Life 1 MDL files in user download directories or shared asset folders

Detection Strategies

Inventory binaries that statically or dynamically link Assimp and identify versions at or below 6.0.4
Inspect crash dumps for fault addresses inside HL1MDLLoader::read_sequence_infos or the aiString copy path
Use file-type telemetry to flag MDL files being parsed by applications outside their normal workflow

Monitoring Recommendations

Monitor endpoint telemetry for repeated crashes of 3D applications correlated with MDL file access
Audit software bill of materials (SBOM) entries for Assimp dependencies across internal toolchains
Track file ingestion events in asset pipelines and content management systems for malformed model files

How to Mitigate CVE-2026-10233

Immediate Actions Required

Identify all internal applications that bundle Assimp and verify the linked version against 6.0.4
Restrict opening of untrusted .mdl files until a patched Assimp build is deployed
Isolate asset-processing workloads in sandboxed or low-privilege environments

Patch Information

At the time of publication, the Assimp project has acknowledged the report and tagged it as a bug. Track the upstream fix through the GitHub Assimp Repository and the corresponding GitHub Issue #6619. Vendors that ship products containing Assimp should monitor for and integrate the upstream patch once released. Additional advisory context is available at VulDB CVE-2026-10233.

Workarounds

Disable the Half-Life 1 MDL importer in build configurations where it is not required
Pre-validate model files with a separate parser or schema check before passing them to Assimp
Run file-conversion utilities under a non-privileged service account with limited filesystem access

bash

# Build Assimp without the Half-Life 1 MDL importer
cmake -DASSIMP_BUILD_MDL_IMPORTER=OFF \
      -DASSIMP_BUILD_ALL_IMPORTERS_BY_DEFAULT=ON \
      -S . -B build
cmake --build build --config Release