---
id: CVE-2026-120755
title: >-
  Integer Underflow Leads to Out-of-Bounds Read via Truncated Chunk in HDF5 Szip
  Filter
summary: >-
  HDF5 through 2.2.0 contains an out-of-bounds read vulnerability in
  H5Z__filter_szip() in src/H5Zszip.c. When decoding a szip-compressed chunk,
  the function subtracts the 4-byte uncompressed-length header from the chunk
  length without fir…
severity: medium
cvss: 4.7
cvssVector: 'CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:P'
cvssSource: cna
cwe:
  - CWE-125
vendor: The HDF Group
product: Szip Filter
affected:
  - szip_filter < 2.3.0
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-03T15:43:28.018929Z'
published: '2026-11-03'
updated: '2026-11-03'
sourceUpdated: '2026-11-03T15:43:43.838Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-120755'
references:
  - url: 'https://github.com/HDFGroup/hdf5/pull/6585'
tags:
  - cve.org
epss: 0.0014
epssPercentile: 0.03367
ingestedAt: '2026-11-05T20:33:06.273Z'
---

## Overview

HDF5 through 2.2.0 contains an out-of-bounds read vulnerability in H5Z__filter_szip() in src/H5Zszip.c. When decoding a szip-compressed chunk, the function subtracts the 4-byte uncompressed-length header from the chunk length without first verifying that the chunk is at least 4 bytes long. A truncated or corrupted chunk shorter than the header causes the length calculation to wrap around to a very large value, and the decompressor reads far past the end of the chunk buffer. An attacker who can get a user or application to read a dataset from a crafted HDF5 file can cause a denial of service. Only builds with szip support (libaec or the szip library) are affected.

## Affected

- `szip_filter < 2.3.0`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.