CVE-2025-6516: HDF5 Heap Buffer Overflow Vulnerability

CVE-2025-6516 Overview

CVE-2025-6516 is a heap-based buffer overflow vulnerability in the HDF5 library through version 1.14.6. The flaw resides in the H5F_addr_decode_len function within /hdf5/src/H5Fint.c. An attacker with local access and low privileges can trigger memory corruption by supplying a crafted HDF5 file. The issue is classified under [CWE-119] (Improper Restriction of Operations within the Bounds of a Memory Buffer) and [CWE-787] (Out-of-bounds Write). A public proof-of-concept has been disclosed, increasing the likelihood of exploitation attempts against applications that parse untrusted HDF5 files.

Critical Impact
Local attackers can corrupt heap memory in processes that parse malicious HDF5 files, potentially affecting confidentiality, integrity, and availability of the host application.

Affected Products

HDF Group HDF5 versions up to and including 1.14.6
Applications embedding the vulnerable libhdf5 library
Scientific computing pipelines that ingest untrusted HDF5 files

Discovery Timeline

2025-06-23 - CVE-2025-6516 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-6516

Vulnerability Analysis

HDF5 is a widely deployed file format and library used across scientific computing, machine learning, and data analytics workloads. The vulnerability affects the H5F_addr_decode_len routine in H5Fint.c, which decodes address values of variable length from an HDF5 file header. When the routine processes a malformed file, it writes past the bounds of an allocated heap buffer.

Because the parser trusts length values embedded in the file, an attacker who controls the input can steer the decoder into writing attacker-influenced bytes outside the intended buffer. The result is heap corruption in the address space of any process that opens the file, such as scientific analysis tools, HDF5 command-line utilities, or Python bindings like h5py.

The EPSS probability is 0.308% (percentile 23.196), reflecting a public proof-of-concept but limited observed exploitation activity.

Root Cause

The root cause is insufficient validation of length and address metadata before decoding. H5F_addr_decode_len does not adequately bound-check the decoded length against the destination buffer, allowing the function to overrun heap allocations while decoding attacker-controlled address fields.

Attack Vector

Exploitation requires local access and the ability to have the target process open a malicious HDF5 file. Common triggers include shared datasets in scientific environments, files transferred through data-exchange workflows, or user-supplied inputs in analytics platforms. No network access or user interaction beyond opening the file is required for the memory corruption to occur.

The vulnerability mechanism is described in the upstream HDF5 GitHub Issue #5581, which also links a reproducer archive. Refer to those references for technical details of the crash trigger.

Detection Methods for CVE-2025-6516

Indicators of Compromise

Crashes or abnormal terminations in processes linked against libhdf5 when opening .h5 or .hdf5 files
Presence of HDF5 files matching the published reproducer archive hash from the upstream issue
Heap corruption signatures in crash dumps referencing H5F_addr_decode_len or H5Fint.c

Detection Strategies

Inventory endpoints and servers for the libhdf5 version using package managers or file version scans, and flag versions at or below 1.14.6
Monitor for processes such as h5dump, h5ls, Python interpreters loading h5py, and MATLAB or Jupyter workers that crash while parsing HDF5 inputs
Inspect newly received HDF5 files with sandboxed parsers before allowing analyst workstations to open them

Monitoring Recommendations

Alert on repeated segmentation faults or ASan/heap-buffer-overflow reports involving HDF5 symbols
Track file-access telemetry for HDF5 files sourced from untrusted collaborators or external portals
Correlate crash telemetry from EDR agents with recent HDF5 file downloads or transfers

How to Mitigate CVE-2025-6516

Immediate Actions Required

Identify all systems and container images shipping libhdf5 versions up to 1.14.6 and prioritize them for upgrade
Restrict opening HDF5 files sourced from untrusted parties until a patched version is deployed
Run HDF5-consuming workloads under least-privilege service accounts to limit blast radius from heap corruption

Patch Information

The HDF Group tracks the fix through HDF5 GitHub Issue #5581. Consult that issue and subsequent HDF5 releases for the corrected version, then upgrade libhdf5 and any statically linked applications. Additional advisory metadata is available at VulDB entry 313636.

Workarounds

Validate HDF5 files in an isolated sandbox or container before opening them on production workstations
Disable or remove HDF5 parsing features in applications that do not require them
Use application allowlists to prevent execution of ad-hoc HDF5 utilities on sensitive hosts

bash

# Check installed HDF5 library version on Linux
h5cc -showconfig | grep -i version
dpkg -l | grep -i libhdf5
rpm -qa | grep -i hdf5