CVE-2026-34734 HDF5: H5T__conv_struct Use After Free
An attacker can trigger a heap use-after-free in the h5dump utility by supplying a malicious HDF5 file, potentially leading to code execution or crashes.
- 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-2026-34734?
CVE-2026-34734 is a high-severity use after free vulnerability in Hdfgroup Hdf5, published on 9 Apr 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
HDF5 is software for managing data. In 1.14.1-2 and earlier, a heap-use-after-free was found in the h5dump helper utility. An attacker who can supply a malicious h5 file can trigger a heap use-after-free. The freed object is referenced in a memmove call from H5T__conv_struct. The original object was allocated by H5D__typeinfo_init_phase3 and freed by H5D__typeinfo_term.
Which versions are affected by CVE-2026-34734?
It affects 1 product.
Products include Hdfgroup Hdf5.
How do I fix CVE-2026-34734?
Upgrade to a fixed version.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-34734 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34734 exists.
Other vulnerabilities in Hdfgroup Hdf5
Sources
Also known as DEBIAN-CVE-2026-34734, ECHO-4587-2d95-fba0, GHSA-w7v2-9cmr-pwwj, JLSEC-2026-354, UBUNTU-CVE-2026-34734.