CVE-2026-10231: Assimp Heap Buffer Overflow in HL1 MDL Loader

Technical summary

CVE-2026-10231 is a heap-based buffer overflow in the HL1MDLLoader::extract_anim_value function within HL1MDLLoader.cpp of Assimp up to version 6.0.4. The vulnerability arises from insufficient bounds checking when the num.total parameter is manipulated during animation value extraction. This allows writing beyond allocated heap memory boundaries, potentially enabling code execution or information disclosure. The flaw is classified under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer) and CWE-122 (Heap-based Buffer Overflow).

Business impact

Organizations using Assimp in 3D graphics pipelines, game engines, visual effects tools, or CAD applications may face data corruption, denial of service, or privilege escalation if a local attacker processes a malicious model file. The impact is most significant in environments where untrusted users have filesystem or process-execution access, or where model files are imported from external sources without validation. Development teams and studios relying on Assimp should assess whether their deployment scenarios permit local attackers to influence model file selection.

Affected systems

Assimp versions up to and including 6.0.4 are confirmed vulnerable. The Half-Life 1 MDL loader component is specifically affected. Any application or tool embedding Assimp for model import functionality may be at risk if users or processes can supply or modify model files. Verify your deployed version against the vendor repository; patch availability should be confirmed through official Assimp release channels.

Exploitability

Public exploit code for this vulnerability has been released, reducing the barrier to weaponization. However, exploitation requires local system access (attacker must already be on the target machine or logged in as a user). The attack does not require elevated privileges initially, though successful exploitation may lead to privilege escalation depending on the host process's context. The relatively straightforward nature of the flaw—once access is granted—and public availability of proof-of-concept code elevates concern for insider threats and compromised-system scenarios.

Remediation

Upgrade Assimp to a patched version beyond 6.0.4. Check the official Assimp GitHub repository for the latest stable release and security patches. If immediate patching is not feasible, restrict local user access to systems running Assimp-dependent applications, limit the sources from which model files are accepted, and implement filesystem monitoring for suspicious model file operations. Additionally, run Assimp-based processes with minimal required privileges.

Patch guidance

Update Assimp to the latest available version from the official repository (verify against vendor advisory for version numbers exceeding 6.0.4). Test patches in a staging environment, particularly for applications in production use where model import is critical. Verify that the patch resolves animation value handling in the HL1MDL loader without breaking existing model import workflows.

Detection guidance

Monitor for unexpected crashes or memory errors in processes using Assimp, especially when processing Half-Life 1 MDL files. Log file access and model import operations; watch for attempts to open suspicious or crafted .mdl files from unusual locations. Heap corruption detectors (e.g., AddressSanitizer in development builds) will flag this flaw if enabled. Endpoint detection and response (EDR) tools should alert on abnormal behavior following model file processing.

Why prioritize this

Although the CVSS score of 5.3 is moderate, the public availability of working exploit code, combined with local-access requirements and potential for privilege escalation, warrants timely remediation. Prioritize patching in multi-user environments, development studios, and systems where model files originate from external or semi-trusted sources. Lower priority in isolated single-user or air-gapped deployments where all model files are internally vetted.

Risk score, explained

The CVSS v3.1 score of 5.3 reflects a Medium severity: the vulnerability requires local attack vector (AV:L), low attack complexity (AC:L), low privileges (PR:L), and no user interaction (UI:N). Impact is limited to the single affected system (S:U) with low confidentiality, integrity, and availability impact (C:L/I:L/A:L). The score does not account for the public exploit availability or potential for post-exploitation privilege escalation, which should factor into organizational risk decisions.

Frequently asked questions