How severe is CVE-2021-42521?

CVE-2021-42521 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-42521 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-42521?

CVE-2021-42521 affects Vtk. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-42521?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-42521 published?

CVE-2021-42521 was published on 2022-08-25 and last updated on 2026-06-17.

CVE-2021-42521

CVE-2021-42521 is a high-severity vulnerability in Vtk with a CVSS 3.x base score of 7.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-476.

Key facts

Severity: High (CVSS 3.x base score 7.5)
EPSS exploit prediction: 1% (61st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-476
Affected product: Vtk
Published: 2022-08-25
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-42521?: 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.
How severe is CVE-2021-42521?: CVE-2021-42521 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-42521 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (61st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-42521?: CVE-2021-42521 affects Vtk. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-42521?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-42521 published?: CVE-2021-42521 was published on 2022-08-25 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:vtk:vtk:*:*:*:*:*:*:*:*

More vulnerabilities in Vtk

CVE-2025-57108 — Critical (CVSS 9.8): Kitware VTK (Visualization Toolkit) through 9.5.0 contains a heap use-after-free vulnerability in…
CVE-2025-57106 — High (CVSS 7.5): Kitware VTK (Visualization Toolkit) up to 9.5.0 is vulnerable to Buffer Overflow in vtkGLTFDocumentLoader. The…
CVE-2025-57107 — High (CVSS 7.1): Kitware VTK (Visualization Toolkit) through 9.5.0 contains a heap buffer overflow vulnerability in…

All CVEs affecting Vtk →

Other CWE-476 (NULL Pointer Dereference) vulnerabilities

CVE-2022-36648 — Critical (CVSS 10.0): The hardware emulation in the of_dpa_cmd_add_l2_flood of rocker device model in QEMU, as used in 7.0.0 and earlier,…
CVE-2020-14500 — Critical (CVSS 10.0): Secomea GateManager all versions prior to 9.2c, An attacker can send a negative value and overwrite arbitrary data.
CVE-2010-2495 — Critical (CVSS 10.0): The pppol2tp_xmit function in drivers/net/pppol2tp.c in the L2TP implementation in the Linux kernel before 2.6.34 does…
CVE-2026-46195 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: smb: client: validate dacloffset before building…
CVE-2026-31657 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: batman-adv: hold claim backbone gateways by…
CVE-2026-31436 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: dmaengine: idxd: fix possible wrong descriptor…

Browse all CWE-476 (NULL Pointer Dereference) vulnerabilities →