# CVE-2026-34734: HDFGroup HDF5 heap use-after-free in h5dump utility

Source: https://junglewise.ai/threats/cve-2026-34734-hdfgroup-hdf5-heap-use-after-free-in-h5dump-utility  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-04-09. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-34734 · Severity: high · CVSS 7.8 · Published 2026-04-09

HDF5 is a data management library used to store and organize large amounts of data. A security flaw in its 'h5dump' utility could allow an attacker to execute malicious code or crash the application if a user is tricked into opening a specially crafted data file. This could lead to a full system compromise or a disruption of operations depending on how the software is used.

Technologies: [Hdfgroup Hdf5](https://junglewise.ai/threats/technologies/hdf5). Vendors: [Hdfgroup](https://junglewise.ai/threats/vendors/hdfgroup).

## Quick answers

**Is CVE-2026-34734 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34734 being exploited in the wild.

**How severe is CVE-2026-34734?** High severity, with a CVSS score of 7.8, published 9 April 2026.

**Which products and versions are affected?** HDFGroup hdf5 <= 1.14.1-2; Red Hat Red Hat Enterprise Linux AI (RHEL AI) 3 affected.

**Is there a fix for CVE-2026-34734?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-34734 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-34734?** Check whether you run Hdfgroup Hdf5. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap use-after-free vulnerability exists in the h5dump helper utility of HDF5 versions 1.14.1-2 and earlier. The flaw occurs when a freed object, originally allocated by H5D__typeinfo_init_phase3 and freed by H5D__typeinfo_term, is subsequently referenced in a memmove call within H5T__conv_struct. An attacker can exploit this by providing a malicious HDF5 (.h5) file. While the primary attack vector requires a user to parse the file with h5dump (UI:R), server-side processes automatically parsing attacker-controlled files may also be at risk. Successful exploitation can lead to arbitrary code execution or a denial-of-service (DoS) condition.

## Affected products

- HDFGroup hdf5 <= 1.14.1-2
- Red Hat Red Hat Enterprise Linux AI (RHEL AI) 3 affected

## Timeline

- 2026-04-09: disclosed: Initial disclosure by HDFGroup and Red Hat
- 2026-04-09: advisory: GitHub Advisory GHSA-w7v2-9cmr-pwwj published

## References

- [https://github.com/HDFGroup/hdf5/security/advisories/GHSA-w7v2-9cmr-pwwj](https://github.com/HDFGroup/hdf5/security/advisories/GHSA-w7v2-9cmr-pwwj)
- [https://access.redhat.com/security/cve/CVE-2026-34734](https://access.redhat.com/security/cve/CVE-2026-34734)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2457034](https://bugzilla.redhat.com/show_bug.cgi?id=2457034)
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34734.json](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34734.json)

## Related threats

- [HDF5 NULL pointer dereference in H5HL_unprotect](https://junglewise.ai/threats/cve-2026-120758-hdf5-through-2-2-0-contains-a-null-pointer-dereference)
- [HDF5 heap buffer over-read in object header deserialization](https://junglewise.ai/threats/cve-2026-120756-hdf5-through-2-2-0-contains-a-heap-buffer-over-read)
- [HDF5 out-of-bounds read in szip filter](https://junglewise.ai/threats/cve-2026-120755-hdf5-through-2-2-0-contains-an-out-of-bounds-read-vulnerability)
- [HDF5 uncontrolled recursion in B-tree iteration](https://junglewise.ai/threats/cve-2026-120689-hdf5-through-2-2-0-contains-an-uncontrolled-recursion)
- [HDFGroup HDF5 heap buffer overflow in H5T__ref_mem_setnull](https://junglewise.ai/threats/cve-2026-29043-hdfgroup-hdf5-heap-buffer-overflow-in-h5t-ref-mem-setnull)