Vulnerability · Published Aug 5, 2026 · Assigned by HDFG
CVE-2026-19027HDF5 out-of-bounds heap read in N-Bit filter decompression
Medium 6.9
In plain English
A medium-severity out-of-bounds read in HDF5 from The HDF Group. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities).
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | hdf5 | no fix listed | DEBIAN-CVE-2026-19027 |
| Debian:13 | hdf5 | no fix listed | DEBIAN-CVE-2026-19027 |
| Debian:14 | hdf5 | no fix listed | DEBIAN-CVE-2026-19027 |
| Ubuntu:22.04:LTS | hdf5 | no fix listed | UBUNTU-CVE-2026-19027 |
| Ubuntu:24.04:LTS | hdf5 | no fix listed | UBUNTU-CVE-2026-19027 |
| Ubuntu:26.04:LTS | hdf5 | no fix listed | UBUNTU-CVE-2026-19027 |
| Ubuntu:26.10 | hdf5 | no fix listed | UBUNTU-CVE-2026-19027 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| The HDF Group | HDF5 | <=2.3.0 |
Weakness: CWE-125 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N