CVE-2026-19028: The Hdf Group HDF5

Medium severity, CVSS 6.8. EPSS: 0.2% chance of exploitation in the next 30 days.

H5Z__filter_fletcher32 in H5Zfletcher32.c in HDF5 prior to 2.3.0 computes the data length to checksum by subtracting the 4-byte trailing checksum size from the input buffer size without checking that the buffer is at least 4 bytes, allowing a size_t underflow. This allows attackers to cause a denial of service (massively out-of-bounds read and application crash in H5_checksum_fletcher32) via a crafted HDF5 file with a Fletcher32-filtered chunk smaller than 4 bytes, triggered via H5Dread, e.g. by the h5ls or h5dump tools.

Affected products

• The Hdf Group HDF5: up to and including 2.3.0

Published 2026-08-06. Last modified 2026-10-06.