CVE-2026-19027
The H5Z__nbit_decompress_one_byte, H5Z__nbit_decompress_one_nooptype, and H5Z__nbit_decompress_one_atomic functions in H5Znbit.c in HDF5 through 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.
CSIRTS triage
- What
- Out-of-bounds heap read in N-Bit Filter decompression can leak sensitive memory.
- Who is affected
- Applications using HDF5 library to process untrusted HDF5 files with N-Bit filters.
- Urgency
- Unknown severity; insufficient details provided but out-of-bounds reads present potential information disclosure risk.
- Action
- Monitor HDF Group security advisories for patches and update HDF5 library when available.
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Exploitation outlook
- Low exploitation risk0.13% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 3% of all EPSS-scored CVEs.
Advisory coverage (2)
- unknownCVE-2026-19027: HDF5 out-of-bounds heap read in N-Bit filter decompressionmsrc · 2026-08-06
- unknownCVE-2026-19027: The H5Z__nbit_decompress_one_byte, H5Z__nbit_decompress_one_nooptype, and H5Z__nbit_decompress…nvd · 2026-08-06
External references
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