CVE-2026-19027: HDF5 out-of-bounds heap read in N-Bit filter decompression

Vulnerability summary

CVE-2026-19027 is a medium (CVSS 6.9) Out-of-bounds Read vulnerability in the hdf group hdf5. EPSS estimates a 0.19% chance of exploitation in the next 30 days, higher than 9.2% of scored vulnerabilities.

Timeline

1. 05-08-2026
   PublishedVulnerability first disclosed.
2. 06-10-2026
   Last modifiedVulnerability information updated.

Description

The H5Z__nbit_decompress_one_byte, H5Z__nbit_decompress_one_nooptype, and H5Z__nbit_decompress_one_atomic functions in H5Znbit.c in HDF5 prior to 2.3.0 advance a read index into the compressed chunk buffer without bounding it against the buffer's actual size. This allows attackers to cause an out-of-bounds heap read, and in constrained cases disclosure of adjacent heap memory into decompressed dataset values, via a crafted HDF5 file whose N-Bit filter parameters describe more decompressed data than the stored compressed chunk actually contains, triggered via H5Dread, e.g. by the h5ls or h5repack tools.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.