# CVE-2026-26199: HDFGroup HDF5 buffer underflow in H5Iget_name

Source: https://junglewise.ai/threats/cve-2026-26199-hdfgroup-hdf5-buffer-underflow-in-h5iget-name  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-20. Updated: 2026-07-20  
License: CC BY 4.0 with a link back

CVE-2026-26199 · Severity: info · CVSS 5.9 · Published 2026-07-20

HDF5 is a high-performance library used for managing and storing large amounts of complex data. A flaw in how the library handles certain name-retrieval requests could allow a crash or memory corruption if a specific parameter is set to zero. This could potentially lead to service instability or application crashes in environments where data processing inputs are not strictly controlled.

## Quick answers

**Is CVE-2026-26199 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-26199 being exploited in the wild.

**How severe is CVE-2026-26199?** Informational severity, with a CVSS score of 5.9, published 20 July 2026.

**Which products and versions are affected?** HDFGroup hdf5 <= 1.14.6.

**Is there a fix for CVE-2026-26199?** 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-2026-26199 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-26199?** Check whether anything you run is named in the advisory. 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 buffer underwrite (CWE-124) exists in the HDF5 library within the H5Iget_name and H5G_get_name functions. When these functions are invoked with a size parameter of 0, the library attempts to place a null terminator in the buffer, leading to a memory underflow. This vulnerability was discovered via fuzzing and requires a specific precondition where an attacker can influence the size parameter passed to the API. An exploit can result in a denial of service (application crash) or corruption of data stored immediately before the intended buffer in memory. The issue is reported to be fixed in version 2.1.0.

## Affected products

- HDFGroup hdf5 <= 1.14.6

## Timeline

- 2026-06-26: advisory: GitHub Security Advisory published
- 2026-07-20: disclosed: CVE published to NVD

## References

- [https://github.com/HDFGroup/hdf5/blob/develop/src/H5Gname.c](https://github.com/HDFGroup/hdf5/blob/develop/src/H5Gname.c)
- [https://github.com/HDFGroup/hdf5/security/advisories/GHSA-5c6x-jmgf-f5vc](https://github.com/HDFGroup/hdf5/security/advisories/GHSA-5c6x-jmgf-f5vc)