CVE-2026-10231: Assimp Buffer Overflow Vulnerability

CVE-2026-10231 Overview

CVE-2026-10231 is a heap-based buffer overflow [CWE-119] in the Open Asset Import Library (Assimp) up to version 6.0.4. The flaw resides in the HL1MDLLoader::extract_anim_value function within HL1MDLLoader.cpp, which implements the Half-Life 1 MDL Loader component. An attacker can manipulate the num.total argument to trigger memory corruption on the heap. The attack requires local access and low privileges. A public proof-of-concept has been released, and the project has tagged the report as a bug.

Critical Impact
Local attackers supplying a crafted Half-Life 1 MDL file can corrupt heap memory in applications using Assimp, potentially leading to crashes or limited code execution within the host process.

Affected Products

Assimp (Open Asset Import Library) versions up to and including 6.0.4
Applications embedding Assimp for 3D model parsing
Half-Life 1 MDL Loader component (HL1MDLLoader.cpp)

Discovery Timeline

2026-06-01 - CVE-2026-10231 published to NVD
2026-06-01 - Last updated in NVD database

Technical Details for CVE-2026-10231

Vulnerability Analysis

The vulnerability exists in the Half-Life 1 MDL Loader component of Assimp, a widely used open-source library for importing 3D model formats. The HL1MDLLoader::extract_anim_value function processes animation values from MDL files but fails to properly validate the num.total argument before performing memory operations. This results in a heap-based buffer overflow when a maliciously crafted MDL file is parsed.

The issue is classified under [CWE-119], improper restriction of operations within the bounds of a memory buffer. Because Assimp is embedded in many 3D modeling tools, game engines, and content pipelines, the attack surface extends to any application that loads untrusted MDL files through the library.

Root Cause

The root cause is insufficient bounds checking on the num.total argument inside extract_anim_value. When an attacker supplies a value that exceeds the size of the destination heap buffer, the loader writes past the allocated region. The Assimp project tracked the issue in GitHub Issue #6616 and tagged it as a bug.

Attack Vector

Exploitation requires local access and the ability to deliver a crafted MDL file to a user or process that invokes the vulnerable Assimp parser. The attacker does not need user interaction beyond the file being loaded by the host application. A public proof-of-concept archive is available, demonstrating the trigger condition.

No verified code samples are available for inclusion. See the GitHub Issue #6616 and the public PoC archive for technical reproduction details.

Detection Methods for CVE-2026-10231

Indicators of Compromise

Unexpected crashes or segmentation faults in applications that import 3D model assets using Assimp
Presence of untrusted .mdl files in user-writable directories that are subsequently processed by 3D tools
Heap corruption traces or AddressSanitizer reports referencing HL1MDLLoader::extract_anim_value in HL1MDLLoader.cpp

Detection Strategies

Inventory applications and build pipelines that link against Assimp 6.0.4 or earlier and flag them for patching
Hash and monitor MDL files introduced from untrusted sources, especially those exceeding expected animation table sizes
Run Assimp-consuming binaries under sanitizers (ASan, HWASan) in development and QA to surface heap overflows tied to malformed MDL inputs

Monitoring Recommendations

Collect process crash telemetry and correlate faulting modules to identify exploitation attempts against Assimp-based parsers
Monitor file-write and execution events for 3D content authoring tools that load externally sourced MDL files
Alert on local users dropping .mdl files into shared asset directories on workstations or build servers

How to Mitigate CVE-2026-10231

Immediate Actions Required

Upgrade Assimp to a version newer than 6.0.4 once an upstream fix is published in the Assimp repository
Restrict loading of MDL files to trusted sources only and block untrusted asset imports in shared environments
Track GitHub Issue #6616 for fix availability and rebuild downstream applications against the patched library

Patch Information

No formal vendor patch reference is listed in the NVD entry at publication time. The maintainers have acknowledged the report via GitHub Issue #6616. Consumers of Assimp should monitor the upstream repository and rebuild dependent applications once a fixed release is tagged. Additional vulnerability context is available at VulDB CVE-2026-10231.

Workarounds

Disable or remove the Half-Life 1 MDL importer in custom Assimp builds if MDL support is not required
Sandbox processes that parse 3D assets so a heap corruption cannot escalate beyond the parsing context
Apply input validation at the application layer to reject MDL files with anomalous animation counts before passing them to Assimp

bash

# Configuration example: build Assimp with the HL1 MDL importer disabled
cmake -DASSIMP_BUILD_MDL_IMPORTER=OFF -DASSIMP_BUILD_TESTS=OFF ..
cmake --build . --config Release