CVE-2026-26197 Array full size, element count, and element size are not checked to make sure they match in H5Odtype.c
A maliciously crafted HDF5 file can trigger an out-of-bounds read due to inconsistent array metadata, potentially exposing memory or causing crashes.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-26197?
CVE-2026-26197 is a medium-severity memory corruption vulnerability in Hdfgroup Hdf5, published on 20 Jul 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
HDF5 is a high-performance library and a file format specification that implements the HDF5 data model. If a file is corrupted such that an array datatype's size, the number of elements, and the element size are not in agreement it can trigger an out of bounds read. The array datatype stores the full size of the datatype (`dt->shared->size`) separately from the number of elements (`dt->shared->u.array.nelem`) and the element size (`dt->shared->parent->shared->size`). If any one of these are corrupted so that they don't align with the others (element size * nelem = full size), it can lead to an out of bounds read. Depending on what is corrupted, it can alter the type of out of bounds read triggered. The vulnerability is present only in files that have been maliciously altered, as its generally not possible to independently alter the full size of the datatype, the element count and the element size. As such, this is only present if a malicious actor is altering files, and won't appear in regular usage.
Weakness: CWE-125
Which versions are affected by CVE-2026-26197?
It affects 1 product.
Products include Hdfgroup Hdf5.
How do I fix CVE-2026-26197?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-26197 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-26197 exists.
Other vulnerabilities in Hdfgroup Hdf5
Sources
Also known as AZL-92847, DEBIAN-CVE-2026-26197, ECHO-e487-ec41-9a0c, GHSA-gh44-7wpq-622f, JLSEC-2026-1162, UBUNTU-CVE-2026-26197.