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CVE.org (no NVD analysis yet)· CNA HDFG

CVE-2026-120756: Heap Buffer Over-read via Malformed Message Size in HDF5's H5O__chunk_deserialize

LowCVSS 1.9 · v4.0—No exploit Fix available

Noroxi assessment

Priority: Monitor (action score 7/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.17% (FIRST EPSS).
  • Someone with local access to the system can trigger it. No account or password is required. No special conditions are required; it is repeatable.
  • Fixed version: azl3 hdf5 1.14.6-6 on Azure Linux 3.0 Release Notes.

Low priority for now. Upgrade to azl3 hdf5 1.14.6-6 on Azure Linux 3.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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 further into the chunk than the size check accounts for. A crafted HDF5 file can declare a message size that passes the check but extends past the end of the chunk image, causing the message’s decode callback, for example H5O__mtime_new_decode() in src/H5Omtime.c, to read beyond the heap allocation. The flaw is reachable during H5Fopen() on a crafted file. An attacker who can get a user or application to open a malicious file can cause a denial of service or limited disclosure of process memory.

Published
Nov 3, 2026
Updated
Nov 3, 2026
EPSS
0.1% · 7th percentile

Report tools

JSON

Action score

7

Monitor

Low priority for now.

CVSS
7 / 40 · 1.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
—
CNA · HDFG
1.9
NVD has not scored this yet; the score shown is the CNA’s.

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

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

If any of these changes, we'll tell you in the daily email digest.

Follow CVE-2026-120756

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

VendorProduct
hdfgrouphdf5

Versions reported by the vendor

Affected version ranges reported by the assigning authority (HDFG). Independent of NVD's CPE analysis and usually ahead of it.

  • The HDF Group HDF5

    • < 2.3.0affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • hdfgroup hdf5up to 2.2.0 inclusive

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12hdf5from 0—

Same product

hdfgroup: all records

Other highest-scoring records for the same primary product.

  • CVE-2018-13876An issue was discovered in the HDF HDF5 1.8.20 library.
    40Plan
  • CVE-2018-13874An issue was discovered in the HDF HDF5 1.8.20 library.
    40Plan
  • CVE-2018-13873An issue was discovered in the HDF HDF5 1.8.20 library.
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-120754Nov 3, 2026 · Uninitialized Heap Memory Disclosure via Truncated Chunk in HDF5 Scale-Offset Filter
    7Monitor
  • ← EarlierCVE-2026-120755Nov 3, 2026 · Integer Underflow Leads to Out-of-Bounds Read via Truncated Chunk in HDF5 Szip Filter
    18Monitor
  • Later →CVE-2026-120757Nov 3, 2026 · Heap Buffer Over-read via Non-Terminated Link Data in H5L__extern_traverse
    27Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
azl3 hdf5 1.14.6-6 on Azure Linux 3.0Release NotesMicrosoft (MSRC)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recorded+8 d
  3. TodayNov 14, 2026+10 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1207570 days apartHeap Buffer Over-read via Non-Terminated Link Data in H5L__extern_traverse
    27Monitor
  • CVE-2026-26197106 days apartArray full size, element count, and element size are not checked to make sure they match in H5Odtype.c
    23Monitor
  • CVE-2026-1757299 days apartHDF5 SOHM List Index Heap Buffer Overflow
    22Monitor
  • CVE-2026-1207550 days apartInteger Underflow Leads to Out-of-Bounds Read via Truncated Chunk in HDF5 Szip Filter
    18Monitor

Not on record for this CVE: researcher credit · public bounty program.

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • No account or password is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
Integrity
Availability
Attack vector
Local
Attack complexity
Low
Privileges required
None
User interaction
P
Scope
X

Weakness class (CWE)

CWE-125 · Out-of-bounds Read

CVSS vector

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/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓
  2. SSVC exploitation— → none
  3. Exploit maturity— → none

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records