CVE-2026-120756: HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.

Q: How do I fix CVE-2026-120756?

hdf5: upgrade to newer than 2.2.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-120756 being exploited?

CVE-2026-120756 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-120756 affect?

CVE-2026-120756 affects hdf5. Severity is medium (CVSS 6.1). HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remain

Q: How urgent is CVE-2026-120756?

Priority 26/100. Public exploit reference

Routine

MEDIUM 6.1UPGRADE

CVE-2026-120756 is a medium-severity flaw (CVSS 6.1) affecting hdf5. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remainder of the message header (flags, and for version 2 object headers, the optional creation index) has been decoded. Because the message body begins after these fields, a message can start up to four bytes furthe

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Local
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	n/a
CISA exploited list	No
Weakness	CWE-125
Published	2026-11-03
Last modified	2026-11-03

Publisher (CNA): HDFG · Vendor: hdfgroup

Last updated 2026-11-03 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-11-03 16:17 UTCPublished CVE record published
2026-11-03 21:09 UTCUpdated Record last modified

hdfgroup hdf5 UPGRADE

Affected: <= 2.2.0

Fixed in: newer than 2.2.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy hdf5 || rpm -q hdf5 || hdf5 --version

2. UPGRADE to newer than 2.2.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade hdf5

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade hdf5

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Advisories and coverage

Research and news

VulDB Recent Entries: CVE-2026-120756 | HDF Group HDF5 up to 2.2.x Object Header Decoding src/H5Ocache.c H5O__chunk_deserialize heap-based overflow 2026-11-03
Vulners Bulletins: CVE-2026-120756 Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize 2026-11-03
Vulners Bulletins: CVE-2026-120756 Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize 2026-11-03

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-120756?

hdf5: upgrade to newer than 2.2.0. Exact commands for each OS are on this page.

Is CVE-2026-120756 being exploited?

CVE-2026-120756 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-120756 affect?

CVE-2026-120756 affects hdf5. Severity is medium (CVSS 6.1). HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5O__chunk_deserialize() in src/H5Ocache.c. When decoding object header messages, the declared message size is checked against the end of the chunk image before the remain

How urgent is CVE-2026-120756?

Priority 26/100. Public exploit reference

Related CVEs

CVE-2026-120754 LOW 3.3 UPGRADE HDF5 through 2.2.0 contains an uninitialized memory read vulnerability in H5Z__filter_scaleoffset() in src/H5Z
CVE-2026-120755 MEDIUM 5.5 UPGRADE HDF5 through 2.2.0 contains an out-of-bounds read vulnerability in H5Z__filter_szip() in src/H5Zszip.c
CVE-2026-120757 HIGH 7.1 UPGRADE HDF5 through 2.2.0 contains a heap buffer over-read vulnerability in H5L__extern_traverse() in src/H5Lexternal
CVE-2026-120758 MEDIUM 5.5 UPGRADE HDF5 through 2.2.0 contains a NULL pointer dereference vulnerability in H5HL_unprotect() in src/H5HL.c
CVE-2026-34734 HIGH 7.8 UPGRADE HDF5 is software for managing data

References

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