CVE-2025-6856 HDF5 H5FL.c H5FL__reg_gc_list use after free
A local attacker can exploit a use-after-free flaw in the HDF5 library to potentially execute arbitrary code or cause a denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-6856?
CVE-2025-6856 is a medium-severity use after free vulnerability in Hdfgroup Hdf5, published on 29 Jun 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A vulnerability, which was classified as problematic, was found in HDF5 1.14.6. Affected is the function H5FL__reg_gc_list of the file src/H5FL.c. The manipulation leads to use after free. Attacking locally is a requirement. The exploit has been disclosed to the public and may be used.
Which versions are affected by CVE-2025-6856?
It affects 1 product.
Products include Hdfgroup Hdf5.
How do I fix CVE-2025-6856?
Apply the vendor's patch.
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-2025-6856 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2025-6856 exists.
Other vulnerabilities in Hdfgroup Hdf5
Sources
Also known as DEBIAN-CVE-2025-6856, ECHO-39a6-65d4-80eb, GHSA-wxfp-rw9f-g4g7, JLSEC-2026-346, UBUNTU-CVE-2025-6856.