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CVE-2026-120756VulnerabilityPublished

Microsoft · Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize

Affects MicrosoftSource GCVE Database

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Authoritative record:CVE-2026-120756· Low 1.9

Public exploit available · CVSS 1.9 Low : upgrade to 2.3.0 as a priority.

Data as of 5 Nov 2026, 09:07 UTC

CVSS 4.0 base score
1.9Low
How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none
CVSS scores by source
CNA (HDFG)CVSS 4.01.9
EPSS
0.1% chance of exploitation in 30 days – higher than 7% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.3.0
CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N/E:P

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 3 Nov 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: evidence found.

    CVSS exploit maturity: proof of concept public

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 5 Nov 2026.

What to do

Upgrade HDF5 and hdfgroup/hdf5 to 2.3.0.

Affected software

ProductAffectedFixed in
The HDF GroupHDF5Affected
  • <2.3.0
Fixed in
  • 2.3.0
GitHubhdfgroup/hdf5pkg:github/hdfgroup/hdf5Other threatsAffected
  • <2.3.0
Fixed in
  • 2.3.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

CVE-2026-120756 is a heap buffer over-read vulnerability in HDF5's H5O__chunk_deserialize function caused by a malformed message size. This flaw could lead to reading memory beyond allocated buffers, potentially causing application crashes or information disclosure.

References

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