CVE-2026-19967

Executive Summary

CVE-2026-19967 identifies a heap-based buffer overflow vulnerability within the Open Asset Import Library (Assimp), specifically in the Assimp::Compression::decompressBlock function located in code/Common/Compression.cpp of commit 17c12da. This flaw allows a remote attacker to trigger memory corruption by manipulating an input file, potentially leading to impacts on confidentiality, integrity, and availability. Public exploit code for this vulnerability has been released, increasing the urgency for affected organizations to monitor for an official patch, which is not yet available.

Technical Analysis

The vulnerability, classified as CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), is a heap-based buffer overflow. It affects the Open Asset Import Library Assimp, specifically identified in commit 17c12da. The core of the flaw resides within the Assimp::Compression::decompressBlock function, located in the code/Common/Compression.cpp file, which is part of the library's file parser component.

An attacker can exploit this vulnerability by crafting a specially malformed compressed input file. When an application linked against the vulnerable Assimp library attempts to process and decompress this malicious file using the decompressBlock function, the crafted data causes the function to write beyond the allocated memory boundaries on the heap. This memory corruption constitutes the heap-based buffer overflow.

The attack vector is classified as "Network" (AV:N), meaning it can be initiated remotely. However, it requires "User Interaction" (UI:R), implying that a user must typically perform an action, such as opening or importing a malicious file, for the attack to succeed. Attack complexity is rated as "Low" (AC:L), suggesting that specialized conditions or extensive technical knowledge beyond the publicly available exploit are not required. No privileges are needed to trigger the vulnerability (PR:N).

The immediate consequence of a heap-based buffer overflow can range from application crashes (denial of service) to more severe outcomes like information disclosure or arbitrary code execution, depending on the overwrite capabilities and subsequent memory layout manipulation. The CVSS score indicates low impacts on confidentiality, integrity, and availability (C:L, I:L, A:L), primarily suggesting potential for crashes, limited data corruption, or minor information leaks rather than immediate full system compromise. The project maintainers were informed via an issue report but have not yet responded, indicating that no official patch is currently available.

Exploitation Scenarios

Exploitation of CVE-2026-19967 involves the delivery and processing of a malicious input file by an application utilizing the vulnerable Assimp library. The presence of publicly released exploit code signifies that specific attack techniques are known and potentially operationalized.

1. Reconnaissance/Target Identification: An attacker identifies potential targets that incorporate the Open Asset Import Library Assimp, specifically commit 17c12da or earlier unpatched versions, into their applications or services. This could involve examining software bills of materials (SBOMs) or passively observing network traffic for indicators of applications processing 3D asset files (e.g., in enterprise 3D modeling studios, game development environments, or applications that render user-submitted models).
2. Triggering the Flaw: The attacker crafts a malicious compressed asset file (e.g., a malformed .obj, .fbx, or .dae file) specifically designed to exploit the heap-based buffer overflow in the Assimp::Compression::decompressBlock function. This file is then delivered to the target through a vector that necessitates user interaction (UI:R), such as an email attachment, a malicious download link, or a manipulated file uploaded to a file-sharing service. When a user opens or imports this file using an application linked to the vulnerable Assimp library, the decompressBlock function within code/Common/Compression.cpp attempts to process the malformed data, leading to a write operation beyond the allocated buffer on the heap.
3. Payload/Execution Method: Upon triggering the heap-based buffer overflow, the attacker's specially crafted input manipulates the heap memory. While the NVD description does not detail specific post-overflow primitives, typical heap overflows can be leveraged to corrupt adjacent data structures, overwrite sensitive pointers (such as function pointers or exception handlers), or introduce attacker-controlled data into critical memory regions. Given the CVSS scores of C:L, I:L, A:L, a common initial outcome might be an application crash or denial of service due to memory corruption, or limited information disclosure from overwritten heap structures. More advanced exploitation techniques could potentially lead to controlled arbitrary code execution within the context of the vulnerable application, though this is not explicitly stated in the vulnerability description.
4. Post-Exploitation Impact: Successful exploitation primarily leads to impacts on the availability of the affected application (e.g., application crashes, system instability). Depending on the specific memory corruption achieved, there could also be a low impact on confidentiality (e.g., leakage of small pieces of process memory) or integrity (e.g., corruption of application data). If arbitrary code execution is achieved, the attacker could further compromise the system, potentially elevating privileges, installing malware, or exfiltrating data, though the CVSS vector suggests these more severe outcomes are less likely or harder to achieve from this specific vulnerability.

Impact Assessment

The impact of CVE-2026-19967 is significant for organizations relying on the Open Asset Import Library (Assimp) to process 3D asset files. As the exploit has been publicly released, the risk of active exploitation is elevated.

Business Impact: Any business or service that incorporates the vulnerable Assimp library (commit 17c12da or prior unpatched versions) into its client-side applications or server-side processing workflows is at risk. This includes industries such as game development, computer-aided design (CAD), virtual reality (VR), augmented reality (AR), 3D content creation, and any web services that allow users to upload and process 3D models. A successful exploit can lead to:

• Service Disruption: Application crashes or system instability can halt critical design, rendering, or content creation workflows, leading to productivity losses and potential financial costs.
• Data Corruption/Loss: Memory corruption could lead to the loss or alteration of in-memory data, impacting the integrity of ongoing work.
• Reputational Damage: For services that process user-uploaded content, a vulnerability leading to client-side compromise or server-side crashes can erode user trust.

Affected Systems: The vulnerability resides directly within the Assimp library. Therefore, any application that is compiled with or dynamically links to the vulnerable Assimp 17c12da commit (or prior unpatched versions) is affected. This includes various desktop applications, potentially some mobile applications, and server-side components that leverage Assimp for asset parsing.

Blast Radius: The blast radius depends on how Assimp is integrated:

• Client-Side Applications: If used in desktop 3D modeling software, game engines, or viewers, the blast radius is primarily confined to the individual user's machine. Exploitation could lead to compromise of that specific workstation, data theft, or further network pivoting.
• Server-Side Applications: If Assimp is used in a server-side context (e.g., for processing uploaded 3D models in a cloud service), the blast radius could be much wider, potentially affecting the integrity and availability of the entire service or underlying infrastructure. The remote attack vector (AV:N) is particularly concerning in such scenarios.

CVSS Subscores Analysis:

• AV:N (Attack Vector: Network): Indicates that the vulnerability is exploitable over a network, making a broad range of remote attacks possible.
• AC:L (Attack Complexity: Low): Suggests that little effort or specialized knowledge is required for a successful attack, facilitating widespread exploitation.
• PR:N (Privileges Required: None): An attacker does not need any prior access or privileges on the target system, simplifying the attack initiation.
• UI:R (User Interaction: Required): A user action (e.g., opening a malicious file) is necessary for the attack to succeed, which acts as a minor mitigating factor compared to zero-click exploits.
• S:U (Scope: Unchanged): The vulnerability's impact is restricted to the resources managed by the vulnerable component, not expanding to other security scopes.
• C:L (Confidentiality Impact: Low): Implies that some information disclosure is possible, but its scope is limited.
• I:L (Integrity Impact: Low): Indicates that limited modification of data is possible, without allowing full control over data integrity.
• A:L (Availability Impact: Low): Suggests that limited interruption of access to or operations of the affected component (e.g., application crash) can occur.

The combination of network attack vector, low attack complexity, no privileges required, and public exploit availability, despite the user interaction requirement and low impact scores, makes this a critical vulnerability requiring immediate attention from affected organizations.

Detection Guidance

Sigma Rule

title: Assimp Library Heap Buffer Overflow via Application Crash (CVE-2026-19967)
id: 5a8e2f0a-b1c3-4d78-9e1e-b7e6c4a6f7d5
status: experimental
description: Detects potential exploitation attempts of CVE-2026-19967 in applications using Open Asset Import Library Assimp.
    This rule looks for application crashes (e.g., access violations, segmentation faults) or error reporting processes
    that occur following the interaction with file types typically parsed by Assimp, indicative of a triggered heap-based buffer overflow.
references:
    - https://nvd.nist.gov/vuln/detail/CVE-2026-19967
author: valtersit.com
date: 2023/10/27
logsource:
    category: process_creation
    product: windows # Windows specific events, adapt for Linux if needed (e.g., /var/log/syslog for crashes)
detection:
    # Look for applications known to use Assimp (examples) or Windows Error Reporting processes
    application_process:
        Image|endswith:
            - '\blender.exe'
            - '\maya.exe'
            - '\3dsmax.exe'
            - '\unity.exe'
            - '\unrealengine.exe'
            - '\vlc.exe'
        EventID: 4688 # Process Create
    
    crash_indicator_process:
        Image|endswith:
            - '\werfault.exe' # Windows Error Reporting process
            - '\drwtsn32.exe' # Dr. Watson debugger
        CommandLine|contains:
            - ' -p ' # WerFault.exe uses -p for PID
            - ' -ip ' # WerFault.exe uses -ip for parent PID
        EventID: 4688

    crash_event:
        # Event IDs related to application errors or crashes
        EventID:
            - 1000 # Application Error
            - 1001 # Windows Error Reporting event
            # EDRs may have custom crash event IDs, integrate as needed.
        # This part requires specific log sources (e.g., AppLocker, Sysmon Process Termination with ExitCode)
        # For generic Windows logs, matching on common crash reporting processes is more robust.
    
    # Heuristic: Monitor for the creation of common 3D asset files in user download/document directories
    # followed by an application crash. This is challenging to do purely in Sigma without a sequence.
    # The primary detection focuses on the crash itself.
    
    condition: application_process or crash_indicator_process
falsepositives:
    - Legitimate application crashes unrelated to exploitation.
    - Other memory corruption issues.
level: high
tags:
    - attack.impact
    - attack.t1499 # Application Crash
    - cve.2026.19967

YARA Rule

rule CVE_2026_19967_Assimp_Vulnerable_Library {
  meta:
    author = "valtersit.com"
    date = "2023-10-27"
    description = "Detects files potentially linked with or containing vulnerable Open Asset Import Library Assimp commit 17c12da."
    reference = "https://nvd.nist.gov/vuln/detail/CVE-2026-19967"
    cve = "CVE-2026-19967"
    severity = "HIGH"
    license = "CC BY-NC 4.0"
  strings:
    // Identify strings that might be present in the vulnerable library binary or debug symbols
    // These strings are explicitly mentioned in the NVD description.
    $s1 = "Assimp::Compression::decompressBlock" ascii wide nocase
    $s2 = "code/Common/Compression.cpp" ascii wide nocase
    $s3 = "Open Asset Import Library" ascii wide nocase
    $s4 = "Assimp" ascii wide nocase
    // Without specific byte patterns of the vulnerable code in commit 17c12da,
    // relying on debug symbols or distinctive library strings is the most reliable approach.
    // Further refinement may involve looking for specific build hashes or version strings
    // if they become available and are embedded in binaries.

  condition:
    uint16(0) == 0x5A4D and // PE executable marker (for Windows binaries)
    ( (1 of ($s1, $s2)) or (all of ($s3, $s4)) )
}

Suricata IDS Rule

# Suricata rule for CVE-2026-19967: Detecting transfers of potential malicious 3D asset files.
# This vulnerability is a heap-based buffer overflow in a file parser library, triggered by a malicious file.
# The attack requires user interaction (UI:R), typically meaning a user opens a downloaded file.
# Without specific exploit payload signatures or known post-exploitation C2 traffic,
# detection focuses on the delivery vector of the likely malicious files.

alert http any any -> any any (msg:"CVE-2026-19967 Assimp - Potential Malicious 3D Asset File Download"; flow:to_client,established;
    file_data; # Instruct Suricata to inspect the file data stream
    # Identify common 3D asset file extensions that Assimp typically parses
    pcre:"/\.(obj|fbx|dae|stl|gltf|glb|3ds|ply|ase)$/i";
    # Consider additional heuristics if specific patterns of malicious files become known,
    # e.g., files with unusual sizes, specific malformed headers, or embedded unusual content.
    # As no specific exploit pattern is provided, detection is currently based on the file type heuristic.
    classtype:attempted-user; sid:20261996701; rev:1;
    )

# Note: This rule will generate false positives if legitimate 3D asset files are frequently downloaded.
# It should be used as an initial alert for further investigation in environments using Assimp-dependent applications.
# More advanced network detection would require specific indicators of compromise (IOCs) from known exploits.

Elastic Detection

/*
  Elastic EQL Rule for CVE-2026-19967 Assimp Heap Buffer Overflow
  This rule aims to detect application crashes (often resulting from heap overflows)
  that are likely associated with applications using the Assimp library.
  It correlates process creation/crash events, optionally with file creation,
  though correlating file creation to a specific process crash can be challenging.
*/
sequence by host.id
  # Step 1: Detect a suspicious file creation event, such as a 3D asset file in a user's download directory.
  # This step adds context but might be noisy without known malicious file patterns.
  [file where event.action == "creation" and file.extension in ("obj", "fbx", "dae", "stl", "gltf", "glb", "3ds", "ply", "ase") and
   file.path : ("C:\\Users\\*\\Downloads\\*", "C:\\Users\\*\\Documents\\*", "/home/*/Downloads/*", "/home/*/Documents/*")]
  # Step 2: Detect a process crash event shortly after. This is the primary indicator.
  then [process where event.category == "process" and event.type == "end" and process.exit_code != 0 and
   (process.executable.name : ("blender.exe", "maya.exe", "3dsmax.exe", "unity.exe", "unrealengine.exe", "vlc.exe") or
    # Also look for crash reporting utilities if they are spawned by the crashed app
    process.executable.name : ("werfault.exe", "drwtsn32.exe") and process.args : ("-p", "-ip") # werfault args to link to a process
   )
  ]
# Time window between file creation and crash can be adjusted, e.g., maxspan=1m for 1 minute

Splunk SPL Query

/*
  Splunk SPL Query for CVE-2026-19967 Assimp Heap Buffer Overflow
  This query identifies potential exploitation attempts of CVE-2026-19967 by looking for
  application crash events in environments utilizing Open Asset Import Library Assimp.
  It correlates process activities with Windows Event Log crash indicators or EDR data.
*/
(index=winlogs OR index=sysmon OR index=edr_logs)
(
    # Identify process creations for applications known to use Assimp (examples)
    (EventCode=4688 AND (Image="*\\blender.exe" OR Image="*\\maya.exe" OR Image="*\\3dsmax.exe" OR Image="*\\unity.exe" OR Image="*\\unrealengine.exe" OR Image="*\\vlc.exe"))
    OR
    # Identify common Windows crash reporting events
    (EventCode IN (1000, 1001, 7, 4690) AND (Image="*\\werfault.exe" OR Image="*\\drwtsn32.exe"))
)
| eval CommandLineLower=lower(CommandLine)
# Filter for keywords indicative of crashes or memory dumps, especially for crash reporter processes
| search (CommandLineLower="*crash*" OR CommandLineLower="*dump*" OR CommandLineLower="*fault*" OR CommandLineLower="*exception*")
| stats count by _time, host, Image, CommandLine, ParentImage, EventCode, process_id, parent_process_id
| rename Image as "Affected Application", CommandLine as "Crash Command Line"
| table _time, host, "Affected Application", "Crash Command Line", ParentImage, EventCode, process_id, parent_process_id
| sort -_time

Wazuh OSSEC Rule

<!--
  Wazuh OSSEC Rule for CVE-2026-19967 Assimp Heap Buffer Overflow
  This rule detects application crash events that are indicative of a heap-based buffer overflow
  in applications leveraging Open Asset Import Library Assimp. It specifically targets Windows Event Log
  IDs associated with application errors and crash reporting processes.
-->
<group name="syslog,windows,">
  <rule id="100010" level="10">
    <if_sid>60000</if_sid> <!-- Base rule for Windows logs, adjust if using specific log collection -->
    <field name="win.system.eventID">^1000$|^1001$|^7$</field> <!-- Application Error, Information, System Errors -->
    <field name="win.eventdata.processName" type="pcre2">
      (blender\.exe|maya\.exe|3dsmax\.exe|unity\.exe|unrealengine\.exe|vlc\.exe)
    </field>
    <description>CVE-2026-19967 Assimp: Potential Application Crash in Assimp-dependent software.</description>
    <mitre>
      <id>T1499</id> <!-- MITRE ATT&CK: Application Crash -->
    </mitre>
    <group>attack,impact,cve_2026_19967,</group>
  </rule>

  <rule id="100011" level="10">
    <if_sid>60000</if_sid>
    <field name="win.system.eventID">^4688$</field> <!-- Process Creation -->
    <field name="win.eventdata.newProcessName" type="pcre2">
      (werfault\.exe|drwtsn32\.exe) <!-- Windows Error Reporting or Dr. Watson processes -->
    </field>
    <field name="win.eventdata.commandLine" type="pcre2">
      (crash|dump|fault|exception) <!-- Keywords indicating a crash event -->
    </field>
    <description>CVE-2026-19967 Assimp: Windows Error Reporting process triggered, possibly due to Assimp vuln.</description>
    <mitre>
      <id>T1499</id>
    </mitre>
    <group>attack,impact,cve_2026_19967,</group>
  </rule>
</group>

Mitigation & Patch Guidance

Given that CVE-2026-19967 is currently unpatched (Patch Confidence: 0/4), organizations must implement immediate mitigations and prepare for future patching.

1. Immediate Mitigations:

   • Strict Input Validation and Sanitization: All applications processing 3D asset files that rely on Open Asset Import Library (Assimp) should implement rigorous validation and sanitization of input files. This includes checks for file integrity, structure, and unexpected content before passing them to the Assimp library. Limit the sources from which such files are accepted.
   • Application Sandboxing/Isolation: Run applications that parse 3D asset files in isolated environments, such as containers or virtual machines, with minimal network access and user privileges. This limits the potential blast radius if the vulnerability is successfully exploited.
   • Enhanced Endpoint Detection and Response (EDR) Monitoring: Increase vigilance for suspicious activities originating from applications that use Assimp. This includes monitoring for unexpected application crashes, memory access violations (e.g., segfaults), unusual child process spawning, or outbound network connections from these applications.
   • User Awareness Training: Educate users about the risks of opening or importing untrusted 3D asset files from unknown or suspicious sources, reinforcing security best practices against phishing and social engineering.

2. Patch/Upgrade Steps:

   • Monitor Vendor Channels: Closely follow the official GitHub repository for Open Asset Import Library (Assimp) and relevant security advisories for an official patch or updated version addressing CVE-2026-19967. The project has been informed, and a response or fix is anticipated.
   • Upgrade Assimp Library: Once a patched version of Assimp (beyond commit 17c12da) is released, immediately plan and execute upgrades for all affected applications and systems. Prioritize critical systems and those exposed to external input.
   • Dependency Auditing: Conduct an inventory of all software dependencies to identify every application or project within the organization that utilizes the Assimp library. This ensures comprehensive patching across the entire software estate.

3. Long-Term Hardening:

   • Secure Software Development Lifecycle (SSDLC): Integrate security-focused practices, including fuzz testing of file parsers, static and dynamic application security testing (SAST/DAST), and code reviews, for any in-house applications that handle untrusted file inputs.
   • Memory Safety Protections: Where compilation options allow, ensure that memory safety mitigations such as Address Space Layout Randomization (ASLR), Data Execution Prevention (DEP), and compiler-provided buffer overflow checks (e.g., stack canaries) are enabled.
   • Principle of Least Privilege: Continuously apply the principle of least privilege to all applications and services, ensuring they operate with only the minimum necessary permissions required for their function.
   • Automated Dependency Scanning: Utilize automated tools to continuously scan project dependencies for known vulnerabilities, reducing reliance on manual tracking.

References

• NVD - CVE-2026-19967: https://nvd.nist.gov/vuln/detail/CVE-2026-19967
• Open Asset Import Library (Assimp) GitHub Project: https://github.com/assimp/assimp
• CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer: https://cwe.mitre.org/data/definitions/119.html

Known Exploit in the Wild Evidence: The NVD description explicitly states: "The exploit has been released to the public and may be used for attacks." This confirms that functional exploit code is publicly available, increasing the urgency for mitigation, although specific threat actor campaigns leveraging this CVE have not been detailed.