CVE-2026-26200: HDF5 Buffer Overflow Vulnerability

CVE-2026-26200 Overview

HDF5 is software for managing scientific data. Prior to version 1.14.4-2, a heap-based buffer overflow vulnerability exists in the HDF5 library that can be triggered when parsing a maliciously crafted .h5 file. An attacker who can control an h5 file parsed by HDF5 can trigger a write-based heap buffer overflow condition. This can lead to a denial-of-service condition, and potentially further issues such as remote code execution depending on the practical exploitability of the heap overflow against modern operating systems. Real-world exploitability of this issue in terms of remote-code execution is currently unknown.

Critical Impact

This heap buffer overflow vulnerability in HDF5 can result in denial of service and potentially remote code execution when processing malicious HDF5 files.

Affected Products

• HDF5 versions prior to 1.14.4-2
• Applications that use the HDF5 library to parse .h5 files
• Scientific computing environments utilizing HDF5 for data management

Discovery Timeline

• 2026-02-19 - CVE CVE-2026-26200 published to NVD
• 2026-02-19 - Last updated in NVD database

Technical Details for CVE-2026-26200

Vulnerability Analysis

This vulnerability is classified as CWE-122 (Heap-based Buffer Overflow). The flaw allows an attacker to craft a malicious HDF5 file that, when parsed by the HDF5 library, triggers a write operation that exceeds the allocated heap buffer boundaries. The vulnerability requires local access and user interaction (opening a malicious file), but requires no privileges to exploit.

The heap buffer overflow occurs during the parsing of HDF5 file structures, where insufficient bounds checking allows data from the file to be written beyond the allocated memory region. This memory corruption can overwrite adjacent heap metadata or application data, leading to unpredictable behavior including crashes or potentially arbitrary code execution.

Root Cause

The root cause of CVE-2026-26200 is insufficient bounds validation in the HDF5 file parsing routines. When processing certain data structures within an HDF5 file, the library fails to properly verify that the data size does not exceed the allocated buffer capacity, allowing a write-based heap overflow condition. This is a classic memory safety issue where input validation does not adequately constrain write operations to their intended memory regions.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to deliver a malicious .h5 file to a victim and convince them to open or process it with an application using the vulnerable HDF5 library. Attack scenarios include:

1. Email attachment delivery - Sending a malicious HDF5 file disguised as legitimate scientific data
2. Data sharing platforms - Uploading crafted files to scientific data repositories
3. Supply chain attacks - Compromising data processing pipelines that automatically process HDF5 files

The vulnerability manifests during file parsing when the HDF5 library processes the maliciously structured file content. For detailed technical information, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-26200

Indicators of Compromise

• Unexpected crashes or segmentation faults in applications using HDF5 library during file parsing operations
• Memory corruption errors or heap-related exceptions when processing .h5 files
• Anomalous process behavior following HDF5 file operations, including unexpected child processes or network connections
• Core dumps indicating heap corruption in HDF5-related functions

Detection Strategies

• Monitor for abnormal process termination patterns in applications that utilize HDF5 for data processing
• Implement file integrity monitoring for HDF5 files received from external sources
• Deploy endpoint detection solutions capable of identifying heap overflow exploitation attempts
• Use memory sanitization tools (AddressSanitizer, Valgrind) during development and testing to detect buffer overflows

Monitoring Recommendations

• Log all HDF5 file parsing operations, including source and file metadata
• Implement sandboxed processing environments for untrusted HDF5 files
• Monitor system call patterns for applications processing external HDF5 data
• Configure SentinelOne to alert on suspicious memory access patterns in HDF5-dependent applications

How to Mitigate CVE-2026-26200

Immediate Actions Required

• Upgrade HDF5 library to version 1.14.4-2 or later immediately
• Audit all systems and applications that utilize HDF5 for data processing
• Restrict processing of HDF5 files from untrusted sources until patching is complete
• Implement input validation for any externally sourced HDF5 files before processing

Patch Information

The HDF Group has released version 1.14.4-2 of HDF5 which addresses this heap buffer overflow vulnerability. Organizations should upgrade to this version or later to remediate CVE-2026-26200. For additional details regarding the fix, consult the GitHub Security Advisory.

Workarounds

• Process HDF5 files in isolated or sandboxed environments to limit potential impact
• Implement strict file source validation and only accept HDF5 files from trusted sources
• Use application-level memory protections such as ASLR and DEP/NX to reduce exploitability
• Consider deploying runtime application self-protection (RASP) solutions for critical HDF5 processing systems

# Verify HDF5 version to ensure patched version is installed
h5cc -showconfig | grep "HDF5 Version"

# Expected output for patched version:
# HDF5 Version: 1.14.4-2 or higher