Vulnerability · Published Aug 5, 2026 · Assigned by HDFG
CVE-2026-19028HDF5 integer underflow in Fletcher32 filter leads to massive out-of-bounds read
Medium 6.8
In plain English
A medium-severity integer overflow in HDF5 from The HDF Group. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 9% of all known vulnerabilities).
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | hdf5 | no fix listed | DEBIAN-CVE-2026-19028 |
| Debian:13 | hdf5 | no fix listed | DEBIAN-CVE-2026-19028 |
| Debian:14 | hdf5 | no fix listed | DEBIAN-CVE-2026-19028 |
| Ubuntu:22.04:LTS | hdf5 | no fix listed | UBUNTU-CVE-2026-19028 |
| Ubuntu:24.04:LTS | hdf5 | no fix listed | UBUNTU-CVE-2026-19028 |
| Ubuntu:26.04:LTS | hdf5 | no fix listed | UBUNTU-CVE-2026-19028 |
| Ubuntu:26.10 | hdf5 | no fix listed | UBUNTU-CVE-2026-19028 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| The HDF Group | HDF5 | <=2.3.0 |
Weakness: CWE-190, CWE-125, CWE-1284 · Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N