CVE-2026-19028 HDF5 integer underflow in Fletcher32 filter leads to massive out-of-bounds read
Attackers can cause denial of service via crafted HDF5 files triggering an integer underflow and out-of-bounds read in the Fletcher32 filter.
- 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-2026-19028?
CVE-2026-19028 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
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.
Which versions are affected by CVE-2026-19028?
How do I fix CVE-2026-19028?
Upgrade to a fixed version.
Is CVE-2026-19028 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19028 exists.
Sources
Also known as AZL-94499, DEBIAN-CVE-2026-19028, ECHO-a9d3-2518-671d, GHSA-2hg9-348w-39gj, UBUNTU-CVE-2026-19028.