# CVE-2026-26200: HDFGroup HDF5 heap buffer overflow in H5T__conv_struct_opt

Source: https://junglewise.ai/threats/cve-2026-26200-hdfgroup-hdf5-heap-buffer-overflow-in-h5t-conv-struct-opt  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-02-19. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-26200 · Severity: high · CVSS 7.8 · Published 2026-02-19

HDF5 is a widely used library and file format for managing and storing large amounts of complex data. A security vulnerability has been identified where a specially crafted data file (.h5) can cause the software to crash or potentially allow an attacker to run unauthorized code. This risk is primarily present when a user is tricked into opening a malicious file or if an automated system processes untrusted data.

Technologies: [Hdfgroup Hdf5](https://junglewise.ai/threats/technologies/hdf5), [Red Hat Enterprise Linux AI (RHEL AI) 3](https://junglewise.ai/threats/technologies/enterprise-linux-ai-3). Vendors: [Hdfgroup](https://junglewise.ai/threats/vendors/hdfgroup), [Red Hat](https://junglewise.ai/threats/vendors/red-hat).

## Quick answers

**Is CVE-2026-26200 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-26200 being exploited in the wild.

**How severe is CVE-2026-26200?** High severity, with a CVSS score of 7.8, published 19 February 2026.

**Which products and versions are affected?** Red Hat Enterprise Linux AI (RHEL AI) 3 affected.

**Is there a fix for CVE-2026-26200?** A patch was published on 2026-02-19: Version 1.14.4-2 released to fix the issue Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-26200 attacked?** It is attacked with local access, in a software library.

**Am I affected by CVE-2026-26200?** Check whether you run Hdfgroup Hdf5 or Red Hat Enterprise Linux AI (RHEL AI) 3 at an affected version. 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-based buffer overflow exists in HDF5 due to an incorrect calculation of buffer size in the H5T__conv_struct_opt method. The vulnerability is triggered when the library parses a maliciously crafted .h5 file, specifically through the h5dump utility or other components using the H5T conversion functions. An attacker can achieve an out-of-bounds write, leading to a denial-of-service (crash) or potentially arbitrary code execution. While the primary attack vector involves local user interaction (opening a file), server-side processes that automatically parse user-supplied HDF5 files are also at risk. The issue is addressed in version 1.14.4-2.

## Affected products

- HDFGroup HDF5 < 1.14.4-2
- Red Hat Red Hat Enterprise Linux AI (RHEL AI) 3 affected

## Timeline

- 2026-02-14: advisory: GitHub advisory published by HDFGroup
- 2026-02-19: disclosed: CVE-2026-26200 published
- 2026-02-19: patched: Version 1.14.4-2 released to fix the issue

## References

- [https://github.com/HDFGroup/hdf5/security/advisories/GHSA-5p2m-j456-9mr2](https://github.com/HDFGroup/hdf5/security/advisories/GHSA-5p2m-j456-9mr2)
- [https://access.redhat.com/security/cve/CVE-2026-26200](https://access.redhat.com/security/cve/CVE-2026-26200)
- [https://bugzilla.redhat.com/show_bug.cgi?id=2441088](https://bugzilla.redhat.com/show_bug.cgi?id=2441088)
- [https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26200.json](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-26200.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)