CVE-2026-19027 HDF5 out-of-bounds heap read in N-Bit filter decompression
Attackers can disclose adjacent heap memory via crafted HDF5 files due to an out-of-bounds read in the N-Bit filter decompression logic.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-19027?
CVE-2026-19027 is a medium-severity vulnerability in The HDF Group HDF5, published on 5 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
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.
Weakness: CWE-125
Which versions are affected by CVE-2026-19027?
How do I fix CVE-2026-19027?
Upgrade to a fixed version.
Is CVE-2026-19027 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19027 exists.
Sources
Also known as AZL-94496, DEBIAN-CVE-2026-19027, ECHO-c165-82fe-ea22, GHSA-2pvh-qgr3-wp2r, UBUNTU-CVE-2026-19027.