CVE-2026-19027Public exploit

Heap over-read via unbounded N-Bit decompression index

Published Aug 5, 2026 · Updated Aug 5, 2026

Out-of-bounds read in HDF5 through 2.3.0 allows attackers to crash file-processing applications or disclose adjacent heap data via crafted files. The H5Z__nbit_decompress_one_byte, H5Z__nbit_decompress_one_nooptype, and H5Z__nbit_decompress_one_atomic functions advance a compressed-buffer index without checking it against the actual chunk length. Processing an untrusted N-Bit-filtered dataset through H5Dread is required; observed results include process crashes, while disclosure is limited to adjacent heap bytes returned as dataset values.

CVSS severity6.9
Medium
EPSS probability0.13%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds read in HDF5 through 2.3.0 allows attackers to crash file-processing applications or disclose adjacent heap data via crafted files. The H5Z__nbit_decompress_one_byte, H5Z__nbit_decompress_one_nooptype, and H5Z__nbit_decompress_one_atomic functions advance a compressed-buffer index without checking it against the actual chunk length. Processing an untrusted N-Bit-filtered dataset through H5Dread is required; observed results include process crashes, while disclosure is limited to adjacent heap bytes returned as dataset values.

The record

CVE
CVE-2026-19027
Published
Aug 5, 2026
Updated
Aug 5, 2026
Vendor
The HDF Group
Product
HDF5
Classifications
CWE-125, T1204.002
Attack vector
local
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=<=2.3.0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesunauthenticated

What is affected?

The HDF Group · HDF5version=<=2.3.0

Published CVSS scores

6.9HDFGCVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1204.002Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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