What’s Vulnerable › Vulnerabilities

CVE-2026-26199: Buffer underflow in `H5Iget_name `/`H5G_get_name` if size is zero

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-07-20 · updated 2026-10-24
• Weakness: CWE-124

Description

HDF5 is a high-performance library and a file format specification that implements the HDF5 data model. If `H5Iget_name` is invoked on a group id with `0` for the size parameter, it will underflow when trying to place a null terminator in the buffer. This can occur if `H5Iget_name` is invoked in a way where `size` can be forced to zero, and there is important data before the `name` buffer.

Affected products

• HDF5: before 2.1.0 — fixed in 2.1.0

How to fix

Upgrade to a fixed version: HDF5 2.1.0. Check the vendor advisory for mitigations.

References

• https://github.com/HDFGroup/hdf5/blob/develop/src/H5Gname.c#L474
• https://github.com/HDFGroup/hdf5/security/advisories/GHSA-5c6x-jmgf-f5vc
• https://github.com/HDFGroup/hdf5/security/advisories/GHSA-5c6x-jmgf-f5vc

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