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CVE Record

CVE-2021-42521: There is a NULL pointer dereference vulnerability in VTK before 9.2.5, and it lies in IO/Infovis/vtkXMLTree...

There is a NULL pointer dereference vulnerability in VTK before 9.2.5, 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.

UnknownCVSS not scoredNot KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

VTK can crash when processing a malformed or empty XML tree document because it dereferences a missing root element. The business impact is mainly service interruption in applications that parse untrusted VTK XML tree input. There is no source evidence of active exploitation in the provided bundle.

Executive priority

Treat this as a targeted reliability and denial-of-service issue, not a broad breach indicator. Prioritize remediation where VTK processes external data or supports critical scientific, visualization, medical, engineering, or analytics workflows.

Technical view

CVE-2021-42521 is a NULL pointer dereference in VTK IO/Infovis/vtkXMLTreeReader.cxx. The code failed to check whether libxml2 xmlDocGetRootElement returned NULL before dereferencing it. Sources describe affected VTK as before 9.2.5, while the affected entry lists VTK 9.0.0 and before.

Likely exposure

Exposure is most likely in applications, pipelines, or services using VTK to parse XML tree data from users, partners, files, or automated feeds. Closed workflows parsing only trusted local data have lower practical exposure.

Exploitation context

The provided sources do not show KEV listing or active exploitation. The plausible impact is application crash or denial of service when vulnerable parsing code handles crafted invalid XML input. No remote code execution evidence is provided.

Researcher notes

Version evidence is incomplete and slightly inconsistent: the description says VTK before 9.2.5, while the affected record lists VTK 9.0.0 and before. Validate against Kitware and downstream Linux distribution advisories before closing exposure.

Mitigation direction

  • Upgrade VTK to 9.2.5 or later where feasible.
  • Check Kitware and distribution advisories for exact fixed package versions.
  • Restrict VTK XML tree parsing to trusted inputs until upgraded.
  • Add operational safeguards for parser crashes in exposed services.

Validation and detection

  • Inventory applications and containers that include VTK.
  • Confirm deployed VTK versions against vendor or distribution package metadata.
  • Identify workflows parsing XML tree data from untrusted sources.
  • Review crash reports for vtkXMLTreeReader or XML parsing failures.
Prepared
Confidence
medium
Sources
5

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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cve · low confidence lookup

CVE-2021-42521 mapping review

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Vulnerability profileCVE Program record
Severity
Unknown
CVSS
Not scored
Known Exploited
No
Published
Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

0CVSS vectors
0Timeline events
0ADP providers
4Source links

CVSS and timeline data

No CVSS vectors or timeline events were available in the normalized CVE source material.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
n/avtkVTK - 9.0.0 and beforeListed
Weakness

CWE details

CWE-400

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CWE-400 · source CWE mapping

Uncontrolled Resource Consumption

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