CVE-2021-42521: Vtk VTK NULL Pointer Dereference Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-xfhg-9pjg-xg7g
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CVSS 7.5
CWE-400 CWE-476
Published
Advisory Summary

CVE-2021-42521 is a HIGH (CVSS 7.5) vtk null pointer dereference vulnerability vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Vtk libraries in the PyPI ecosystem. The issue involves vtk null pointer dereference vulnerability. Remediation is available by upgrading affected packages to version 9.0.1.

CVE-2021-42521 at a Glance

CVE Identifier CVE-2021-42521
GHSA Identifier GHSA-xfhg-9pjg-xg7g
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Vtk
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2021-42521

To remediate this vulnerability, upgrade all affected Vtk dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

vtk fixed: 9.0.1 
pip install vtk>=9.0.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show vtk

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2021-42521, inspect your installed packages using pip:

pip show vtk

Analyze the terminal output to locate any version of Vtk in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 9.0.1), your application is affected.

Note: The pip show vtk command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Vtk, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

There is a NULL pointer dereference vulnerability in VTK, and it lies in IO/Infovis/vtkXMLTreeReader.cxx. The vendor didn't check the return value of libxml2 API 'xmlDocGetRootElement', and try to dereference it. It is unsafe as the return value can be NULL and that NULL pointer dereference may crash the application.

CVE-2021-42521 Affected Vtk Versions

1 component(s)
Fixed Versions:
9.0.1
Product / Package Ecosystem Affected Versions Fixed Version
vtk
pypi/vtk
PyPI
< 9.0.1
9.0.1

References

NVD — CVE-2021-42521 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-42521
Vtk Security Information SECURITY
https://discourse.vtk.org/t/vtk-9-2-5-is-out/10549
Vtk Source Repository REPOSITORY
https://github.com/pypa/advisory-database/tree/main/vulns/vtk/PYSEC-2022-255.yaml
gitlab.kitware.com/vtk/vtk PACKAGE
https://gitlab.kitware.com/vtk/vtk
gitlab.kitware.com/vtk/vtk/issues/1781... WEB
https://gitlab.kitware.com/vtk/vtk/issues/17818
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PCTMSAAVP4BW2HTZLDWMGKZ2WEC5OFLK

Frequently Asked Questions

What is CVE-2021-42521?
CVE-2021-42521 is a security vulnerability in Vtk involving VTK NULL pointer dereference vulnerability under CWE-400: Uncontrolled Resource Consumption.
Which Vtk versions are affected?
Affected versions include releases prior to 9.0.1 across affected packages: vtk.
What version fixes CVE-2021-42521?
Upgrading to 9.0.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is vtk affected?
Yes, vtk is affected in releases prior to 9.0.1. Upgrade your dependency to 9.0.1 or later.
What is the CVSS score of CVE-2021-42521?
CVE-2021-42521 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-42521?
CVE-2021-42521 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check PyPI dependencies for CVE-2021-42521?
Run the dependency tree command: 'pip show vtk'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-xfhg-9pjg-xg7g",
  "modified" : "2024-11-18T23:03:45Z",
  "published" : "2022-08-26T00:03:30Z",
  "aliases" : [ "CVE-2021-42521" ],
  "summary" : "VTK NULL pointer dereference vulnerability",
  "details" : "There is a NULL pointer dereference vulnerability in VTK, and it lies in IO/Infovis/vtkXMLTreeReader.cxx. The vendor didn't check the return value of libxml2 API 'xmlDocGetRootElement', and try to dereference it. It is unsafe as the return value can be NULL and that NULL pointer dereference may crash the application.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "vtk"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "9.0.1"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-42521"
  }, {
    "type" : "WEB",
    "url" : "https://discourse.vtk.org/t/vtk-9-2-5-is-out/10549"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pypa/advisory-database/tree/main/vulns/vtk/PYSEC-2022-255.yaml"
  }, {
    "type" : "PACKAGE",
    "url" : "https://gitlab.kitware.com/vtk/vtk"
  }, {
    "type" : "WEB",
    "url" : "https://gitlab.kitware.com/vtk/vtk/issues/17818"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/PCTMSAAVP4BW2HTZLDWMGKZ2WEC5OFLK"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-476" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-09-16T18:47:42Z",
    "nvd_published_at" : "2022-08-25T18:15:00Z"
  }
}