CVE-2025-6857: HDF5 Buffer Overflow Vulnerability

CVE-2025-6857 Overview

CVE-2025-6857 is a stack-based buffer overflow vulnerability in HDF5 version 1.14.6, a widely used scientific data format library maintained by The HDF Group. The flaw resides in the H5G__node_cmp3 function within src/H5Gnode.c. An attacker with local access and low privileges can trigger the overflow by supplying a crafted HDF5 file, causing memory corruption and process instability. The exploit technique has been publicly disclosed, increasing the risk of opportunistic use against applications that parse untrusted HDF5 files. The issue is tracked under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).

Critical Impact
Local attackers can corrupt process memory in applications parsing untrusted HDF5 files, leading to denial of service and potential further exploitation.

Affected Products

HDF Group HDF5 version 1.14.6
Applications and scientific computing pipelines that link against the affected HDF5 release
Downstream language bindings (C, C++, Fortran, Python) that use the vulnerable H5Gnode.c code path

Discovery Timeline

2025-06-29 - CVE-2025-6857 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-6857

Vulnerability Analysis

The vulnerability affects the H5G__node_cmp3 comparison function used internally by HDF5 when traversing B-tree nodes representing group entries. HDF5 organizes group metadata in B-tree structures, and H5G__node_cmp3 compares a search key against entries stored in a node. Malformed node data on the stack can exceed expected bounds, corrupting adjacent stack memory during comparison operations. Because the corruption occurs on the stack, it can overwrite saved return addresses, frame pointers, or local variables used later in the parsing routine. The result is typically a process crash, though carefully constructed input could influence control flow depending on compiler mitigations in place.

Root Cause

The root cause is insufficient bounds checking within src/H5Gnode.c when the H5G__node_cmp3 function processes group node key data read from an HDF5 file. Trusted length assumptions about the on-disk key structure allow attacker-controlled sizes to influence stack buffer operations, satisfying the conditions of [CWE-119].

Attack Vector

Exploitation requires local access and a low-privileged account. The attacker delivers a crafted HDF5 file to a user or automated process that opens it with a vulnerable HDF5 library build. When the library traverses the malicious group B-tree, H5G__node_cmp3 executes with attacker-influenced key data and overflows its stack buffer. No user interaction beyond opening the file is required for the code path to trigger. Public disclosure of the crash reproducer, referenced in the GitHub HDF5 Crash Log, lowers the barrier for creating working proofs of concept.

See the upstream GitHub Issue Report for a full reproducer and stack trace.

Detection Methods for CVE-2025-6857

Indicators of Compromise

Unexpected crashes or segmentation faults in processes linked against libhdf5 version 1.14.6, particularly with stack traces containing H5G__node_cmp3 or H5Gnode.c.
HDF5 files (.h5, .hdf5) received from untrusted sources or arriving via unusual delivery channels such as web uploads or email attachments.
Core dumps in scientific computing, HPC, or data-analysis workloads that reference the HDF5 group B-tree traversal path.

Detection Strategies

Inventory installed HDF5 libraries across endpoints and build environments; flag hosts running version 1.14.6.
Enable Address Sanitizer (ASan) or stack canary reporting in development builds to catch overflow attempts during file ingestion tests.
Monitor process telemetry for repeated abnormal terminations of applications known to use HDF5, correlating with recent file-open events.

Monitoring Recommendations

Aggregate crash reports and core dump metadata into a central log platform to identify clusters of HDF5-related failures.
Track file provenance for HDF5 inputs used by scheduled batch jobs and analytics pipelines.
Alert on execution of HDF5-consuming binaries from non-standard user directories or temp paths.

How to Mitigate CVE-2025-6857

Immediate Actions Required

Identify all systems running HDF5 1.14.6 and restrict processing of HDF5 files sourced from outside the organization.
Isolate HDF5 parsing workloads in sandboxed or containerized environments with non-privileged accounts and no network egress.
Review the upstream GitHub Issue Report for status updates on an official fix and monitor for a patched release.

Patch Information

At the time of publication, no vendor-assigned patched release for CVE-2025-6857 is listed in the enriched CVE data. Track the HDF Group HDF5 GitHub repository and the referenced issue #5575 for a corrected build. Rebuild and redeploy dependent applications after upgrading.

Workarounds

Validate HDF5 input files with a schema or metadata sanity check before passing them to the vulnerable library.
Run HDF5-consuming processes under least privilege, with reduced OS capabilities and mandatory access controls such as SELinux or AppArmor.
Enable compiler-level stack protections (-fstack-protector-strong, -D_FORTIFY_SOURCE=2, and Position Independent Executables) when building HDF5 and its consumers from source.

bash

# Configuration example: identify HDF5 1.14.6 installations on Linux hosts
ldconfig -p | grep -i libhdf5
find / -name 'libhdf5*' 2>/dev/null -exec sh -c 'strings "$1" | grep -E "HDF5 library version: 1\.14\.6"' _ {} \;