CVE-2025-6818: HDF Group HDF5 Buffer Overflow Vulnerability

CVE-2025-6818 Overview

CVE-2025-6818 is a heap-based buffer overflow vulnerability in the Hierarchical Data Format version 5 (HDF5) library, release 1.14.6. The flaw resides in the H5O__chunk_protect function within /src/H5Ochunk.c. An attacker with local, low-privilege access can trigger memory corruption by supplying a crafted HDF5 file that mishandles object header chunk boundaries. Public disclosure of the issue includes a crash reproducer, which raises the likelihood of opportunistic exploitation against applications that ingest untrusted HDF5 files. The vulnerability is tracked under CWE-119: Improper Restriction of Operations within the Bounds of a Memory Buffer.

Critical Impact
A local attacker can craft an HDF5 file that corrupts heap memory during object header parsing, resulting in application crashes and potential availability impact for scientific and data-processing workflows.

Affected Products

HDF Group HDF5 version 1.14.6
Applications and language bindings that link against the affected HDF5 library
Scientific data pipelines and analytics tools that parse untrusted .h5 / .hdf5 files

Discovery Timeline

2025-06-28 - CVE-2025-6818 published to NVD with public disclosure referenced in HDF5 GitHub Issue #5573
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-6818

Vulnerability Analysis

The defect sits in H5O__chunk_protect, an internal routine responsible for protecting (pinning in cache) an object header chunk before subsequent read or modify operations. HDF5 object headers are split into chunks, each described by size and offset metadata stored in the file. When the library trusts attacker-controlled chunk metadata without adequate validation, downstream operations can read or write past the heap buffer allocated for the chunk.

Because the vulnerable code path executes during standard file open and object traversal operations, any application that opens a malicious HDF5 file inherits the flaw. Impact centers on availability: heap corruption reliably crashes the host process. The vendor advisory does not confirm code execution, and the CVSS 4.0 vector reports only limited availability impact with no confidentiality or integrity effect.

Root Cause

The root cause is improper restriction of operations within the bounds of a memory buffer during object header chunk protection. Chunk size or offset fields sourced from the file are used in memory operations without sufficient sanity checks against the actual allocation, producing an out-of-bounds heap access. Corroborating crash output is provided in the reporter's crash artifact.

Attack Vector

Exploitation is local and requires low privileges. The attacker delivers a crafted HDF5 file to a target user or automated pipeline. When the victim application invokes HDF5 APIs such as H5Fopen or object traversal calls, the library reaches H5O__chunk_protect and processes the malformed chunk metadata. No user interaction beyond opening the file is required, and no network vector exists. The vulnerability manifests during parsing of object header chunk metadata; see the HDF5 GitHub Issue #5573 for the reproducer and stack context.

Detection Methods for CVE-2025-6818

Indicators of Compromise

Repeated crashes or SIGABRT/SIGSEGV signals in processes linking libhdf5 version 1.14.6, particularly with stack frames referencing H5O__chunk_protect or H5Ochunk.c.
Untrusted .h5, .hdf5, or .he5 files arriving from external sources, email attachments, or shared datasets.
AddressSanitizer or Valgrind reports indicating heap-buffer-overflow in the HDF5 object header code path.

Detection Strategies

Inventory hosts and container images to identify installations of hdfgroup:hdf5:1.14.6 using software composition analysis or ldd/package manager queries.
Instrument high-risk parsers (data ingest workers, Jupyter kernels, HPC job runners) with ASan or hardened allocators to surface corruption early.
Correlate application crash telemetry with recent file ingestion events to isolate malicious inputs.

Monitoring Recommendations

Collect and centralize process crash and core dump events from systems that process HDF5 files.
Monitor file upload paths and shared data stores for HDF5 files originating from untrusted sources.
Alert on unexpected termination of long-running scientific or analytics workloads that consume external HDF5 datasets.

How to Mitigate CVE-2025-6818

Immediate Actions Required

Restrict processing of HDF5 files to trusted sources until an upstream fix is applied.
Isolate HDF5 parsing workloads in sandboxes, containers, or non-privileged service accounts to contain crash impact.
Track the status of HDF5 GitHub Issue #5573 for an official patched release and apply updates promptly.

Patch Information

At publication, no fixed HDF5 release is referenced in the NVD entry or vendor advisory fields. Monitor the HDF Group HDF5 repository and downstream distribution channels for a version superseding 1.14.6 that addresses H5O__chunk_protect. Additional context is available via VulDB entry #314256.

Workarounds

Validate HDF5 file provenance and integrity, for example using cryptographic signatures or hashes, before invoking any HDF5 API.
Run HDF5-consuming applications under a memory-hardened allocator or with seccomp/AppArmor profiles that limit blast radius on crash.
Where feasible, downgrade to a prior HDF5 release that is unaffected by the H5O__chunk_protect regression, after validating compatibility with dependent tooling.

bash

# Configuration example: identify affected HDF5 installations on Linux hosts
dpkg -l | grep -i hdf5
rpm -qa | grep -i hdf5
find / -name 'libhdf5*' -type f 2>/dev/null -exec sh -c 'strings "$1" | grep -E "HDF5 library version: 1\.14\.6" && echo AFFECTED: $1' _ {} \;