CVE-2026-10232

Executive Summary

CVE-2026-10232 is a Use After Free (UAF) vulnerability identified in the Assimp library, specifically within the ASE file parser component. The flaw resides in the aiNode::~aiNode destructor within scene.cpp. An attacker can trigger this vulnerability by providing a specially crafted ASE file, leading to a use-after-free condition. This can result in a denial of service (DoS) or potentially arbitrary code execution in the context of the application using the library. The vulnerability is classified as local (requiring user interaction to open a malicious file) and has a CVSS score of 5.3 (Medium). The project has acknowledged this as a bug, but no official patch has been released as of the latest analysis.

Supply Chain & Package Security

Assimp is a widely used library for importing various 3D model formats. It is integrated into numerous applications, game engines, and tools. This vulnerability poses a supply chain risk, as any application that uses the vulnerable version of Assimp (up to 6.0.4) and processes user-supplied ASE files could be exploited. The attack vector is local, requiring the victim to open a malicious file, but the impact can be severe if the application runs with elevated privileges or processes files from untrusted sources.

CVSS Breakdown & Threat Level

• CVSS Score: 5.3 (Medium)
• Attack Vector (AV): Local (AV:L) - The attacker must have local access or trick a user into opening a malicious file.
• Attack Complexity (AC): Low (AC:L) - No special conditions are required for exploitation.
• Privileges Required (PR): None (PR:N) - No authentication is needed.
• User Interaction (UI): Required (UI:R) - The victim must open the malicious file.
• Scope (S): Unchanged (S:U) - The vulnerability does not affect resources beyond the vulnerable component.
• Confidentiality (C): None (C:N) - No direct data exposure.
• Integrity (I): None (I:N) - No data modification.
• Availability (A): High (A:H) - Successful exploitation can cause a crash or denial of service.

Threat Level: Medium. The requirement for user interaction and local access reduces the immediate risk, but the public availability of exploit details and the lack of a patch increase the urgency for mitigation.

Deep Dive & Mechanics

The vulnerability is a classic Use After Free (UAF) in the aiNode::~aiNode destructor. When an ASE file is parsed, the library creates a tree of aiNode objects. The destructor is responsible for cleaning up child nodes. The flaw occurs when the destructor attempts to access a child node that has already been freed due to improper handling of the node hierarchy during parsing of a malformed ASE file.

Technical Flow:

1. A user opens a specially crafted ASE file.
2. The ASE parser (ASELoader) creates aiNode objects and links them.
3. Due to a parsing error or malformed data, a child node is freed prematurely (e.g., via an exception or incorrect reference counting).
4. The parent node's destructor (aiNode::~aiNode) is called, which iterates over its children.
5. The destructor accesses the already-freed child node, leading to a use-after-free condition.
6. This can cause a crash (DoS) or, if the freed memory is reallocated with attacker-controlled data, potentially lead to code execution.

The vulnerability is triggered locally, meaning the attacker must convince the user to open the malicious file.

Vulnerable vs. Patched Code

Vulnerable Code (Assimp <= 6.0.4): The vulnerable code is in scene.cpp within the aiNode::~aiNode destructor. The destructor likely iterates over mChildren and deletes them without proper null checks or reference counting.

// Vulnerable snippet (conceptual)
aiNode::~aiNode() {
    for (unsigned int i = 0; i < mNumChildren; ++i) {
        delete mChildren[i]; // Potential UAF if mChildren[i] was already freed
    }
    delete[] mChildren;
}

Patched Code (Hypothetical): A patch would involve adding null checks and ensuring that child nodes are not freed before the parent destructor is called. Additionally, using smart pointers or reference counting could prevent premature deallocation.

// Patched snippet (conceptual)
aiNode::~aiNode() {
    for (unsigned int i = 0; i < mNumChildren; ++i) {
        if (mChildren[i]) {
            delete mChildren[i];
            mChildren[i] = nullptr;
        }
    }
    delete[] mChildren;
    mChildren = nullptr;
}

Note: No official patch has been released. The above is a hypothetical fix.

Exploitation & Lab Setup

Red Team (Exploitation)

Prerequisites:

• A vulnerable version of Assimp (<= 6.0.4).
• A target application that uses Assimp to load ASE files.
• A crafted ASE file that triggers the UAF.

Exploitation Steps:

1. Craft Malicious ASE File: Create an ASE file with a malformed node hierarchy that causes a child node to be freed prematurely. This can be done by manipulating the *SCENE and *GEOMOBJECT blocks.
2. Deliver the File: Use social engineering to trick the user into opening the file in a vulnerable application (e.g., a 3D viewer, game, or tool).
3. Trigger the Vulnerability: When the application parses the file, the UAF occurs, leading to a crash or potential code execution.

Example Malicious ASE Structure (Conceptual):

*3DSMAX_ASCIIEXPORT 200
*COMMENT "Exploit"
*SCENE {
  *SCENE_FILENAME "exploit.ase"
  *SCENE_FIRSTFRAME 0
  *SCENE_LASTFRAME 100
  *SCENE_FRAMESPEED 30
  *SCENE_TICKSPERFRAME 160
  *SCENE_BACKGROUND_STATIC 0.0000 0.0000 0.0000
  *SCENE_AMBIENT_STATIC 0.0000 0.0000 0.0000
}
*MATERIAL_LIST {
  *MATERIAL_COUNT 1
  *MATERIAL 0 {
    *MATERIAL_NAME "Material"
    *MATERIAL_CLASS "Standard"
    *MATERIAL_AMBIENT 0.5882 0.5882 0.5882
    *MATERIAL_DIFFUSE 0.5882 0.5882 0.5882
    *MATERIAL_SPECULAR 0.9000 0.9000 0.9000
    *MATERIAL_SHINE 0.5000
    *MATERIAL_SHINESTRENGTH 0.0000
    *MATERIAL_TRANSPARENCY 0.0000
    *MATERIAL_WIRESIZE 1.0000
    *MATERIAL_SHADING Blinn
    *MATERIAL_XP_FALLOFF 0.0000
    *MATERIAL_SELFILLUM 0.0000
    *MATERIAL_FALLOFF In
    *MATERIAL_XP_TYPE Filter
  }
}
*GEOMOBJECT {
  *NODE_NAME "ExploitNode"
  *NODE_TM {
    *NODE_NAME "ExploitNode"
    *INHERIT_POS 0 0 0
    *INHERIT_ROT 0 0 0
    *INHERIT_SCL 0 0 0
    *TM_ROW0 1.0000 0.0000 0.0000
    *TM_ROW1 0.0000 1.0000 0.0000
    *TM_ROW2 0.0000 0.0000 1.0000
    *TM_ROW3 0.0000 0.0000 0.0000
  }
  *MESH {
    *MESH_NUMVERTEX 3
    *MESH_NUMFACES 1
    *MESH_VERTEX_LIST {
      *MESH_VERTEX 0 0.0 0.0 0.0
      *MESH_VERTEX 1 1.0 0.0 0.0
      *MESH_VERTEX 2 0.0 1.0 0.0
    }
    *MESH_FACE_LIST {
      *MESH_FACE 0: A: 0 B: 1 C: 2 AB: 1 BC: 1 CA: 1 *MESH_SMOOTHING 1 *MESH_MTLID 0
    }
  }
  *MATERIAL_REF 0
}

Note: The exact malformed data to trigger the UAF is not publicly detailed. The above is a template for a valid ASE file.

Blue Team (Detection & Defense)

Detection:

• Monitor for crashes in applications using Assimp when processing ASE files.
• Use file integrity monitoring to detect the introduction of suspicious ASE files.
• Implement behavioral analysis to detect unusual memory access patterns.

Defense:

• Isolate: Run applications that process untrusted 3D files in a sandboxed environment.
• Update: Monitor for patches from the Assimp project and apply them immediately.
• Input Validation: Implement strict validation of ASE files before passing them to the library.
• Alternative Libraries: Consider using alternative 3D model importers that are not affected.

Indicators of Compromise (IOCs)

• File Hashes: (None provided, but users should monitor for suspicious ASE files)
• Process Behavior: Application crashes with access violation errors in aiNode::~aiNode or scene.cpp.
• Network Traffic: None (local vulnerability).
• Registry/File System: Presence of malicious ASE files in user directories or application data folders.

Detection Engineering

YARA Rule

rule CVE_2026_10232_Assimp_UAF {
    meta:
        description = "Detects potential exploitation of CVE-2026-10232 in Assimp via malicious ASE files"
        author = "Valters IT"
        date = "2026-01-01"
        reference = "CVE-2026-10232"
        hash = "unknown"
    strings:
        $ase_header = "*3DSMAX_ASCIIEXPORT"
        $node_name = "*NODE_NAME"
        $geomobject = "*GEOMOBJECT"
        $suspicious_pattern = { 2A 4E 4F 44 45 5F 4E 41 4D 45 } // "*NODE_NAME" in hex
    condition:
        $ase_header at 0 and $geomobject and #suspicious_pattern > 5
}

Sigma Rule

title: CVE-2026-10232 - Assimp ASE File Use After Free
id: 7a8b9c0d-1e2f-3a4b-5c6d-7e8f9a0b1c2d
status: experimental
description: Detects crashes or access violations related to Assimp's scene.cpp when processing ASE files.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-10232
author: Valters IT
date: 2026-01-01
logsource:
    category: application
    product: assimp
detection:
    selection:
        EventID: 1000 (Application Error)
        Application: "*assimp*"
        FaultModule: "*scene.cpp*"
        ExceptionCode: 0xc0000005 (Access Violation)
    condition: selection
falsepositives:
    - Legitimate crashes due to other bugs
level: high

Suricata Rule

alert tcp $HOME_NET any -> $EXTERNAL_NET any (msg:"CVE-2026-10232 - Assimp ASE File Transfer Detected"; flow:to_server; content:"*3DSMAX_ASCIIEXPORT"; nocase; content:"*GEOMOBJECT"; nocase; content:"*NODE_NAME"; nocase; classtype:attempted-dos; sid:1000001; rev:1;)

Note: The Suricata rule is for network detection of ASE file transfers. Since the vulnerability is local, this rule is for monitoring file downloads.

Remediation & Mitigation

Immediate Actions:

1. Isolate: Do not open ASE files from untrusted sources in applications using Assimp <= 6.0.4.
2. Monitor: Watch for official patches from the Assimp project (https://github.com/assimp/assimp).
3. Workaround: If possible, disable ASE file parsing in your application or use a different library.

Long-Term Fix:

• Apply the official patch once released.
• Update to a patched version of Assimp (future release > 6.0.4).
• Implement input validation and sanitization for all 3D model files.

Valters IT Signature

This report was generated by Valters IT Cyber Threat Intelligence. For more information, visit https://valters-it.com.