How severe is CVE-2026-34734?

CVE-2026-34734 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-34734 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-34734?

CVE-2026-34734 affects Hdfgroup Hdf5. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-34734?

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.

Does CVE-2026-34734 have an EU (EUVD) identifier?

Yes. CVE-2026-34734 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-21020.

When was CVE-2026-34734 published?

CVE-2026-34734 was published on 2026-04-09 and last updated on 2026-06-30.

CVE-2026-34734

CVE-2026-34734 is a high-severity vulnerability in Hdfgroup Hdf5 with a CVSS 3.x base score of 7.8. 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-416.

Key facts

Severity: High (CVSS 3.x base score 7.8)
EPSS exploit prediction: 0% (9th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-21020
Weakness: CWE-416
Affected product: Hdfgroup Hdf5
Published: 2026-04-09
Last modified: 2026-06-30

Description

HDF5 is software for managing data. In 1.14.1-2 and earlier, a heap-use-after-free was found in the h5dump helper utility. An attacker who can supply a malicious h5 file can trigger a heap use-after-free. The freed object is referenced in a memmove call from H5T__conv_struct. The original object was allocated by H5D__typeinfo_init_phase3 and freed by H5D__typeinfo_term.

Frequently asked questions

What is CVE-2026-34734?: HDF5 is software for managing data. In 1.14.1-2 and earlier, a heap-use-after-free was found in the h5dump helper utility. An attacker who can supply a malicious h5 file can trigger a heap use-after-free. The freed object is referenced in a memmove call from H5T__conv_struct. The original object was allocated by H5D__typeinfo_init_phase3 and freed by H5D__typeinfo_term.
How severe is CVE-2026-34734?: CVE-2026-34734 has a CVSS 3.x base score of 7.8, rated high severity. It is exploitable over local access with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-34734 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (9th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-34734?: CVE-2026-34734 affects Hdfgroup Hdf5. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-34734?: 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.
Does CVE-2026-34734 have an EU (EUVD) identifier?: Yes. CVE-2026-34734 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-21020.
When was CVE-2026-34734 published?: CVE-2026-34734 was published on 2026-04-09 and last updated on 2026-06-30.

References

Affected products (1)

cpe:2.3:a:hdfgroup:hdf5:*:*:*:*:*:*:*:*

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