CVE-2026-26197

What it is

HDF5 is a high-performance library and a file format specification that implements the HDF5 data model. If a file is corrupted such that an array datatype's size, the number of elements, and the element size are not in agreement it can trigger an out of bounds read. The array datatype stores the full size of the datatype (`dt->shared->size`) separately from the number of elements (`dt->shared->u.array.nelem`) and the element size (`dt->shared->parent->shared->size`). If any one of these are corrupted so that they don't align with the others (element size * nelem = full size), it can lead to an out of bounds read. Depending on what is corrupted, it can alter the type of out of bounds read triggered. The vulnerability is present only in files that have been maliciously altered, as its generally not possible to independently alter the full size of the datatype, the element count and the element size. As such, this is only present if a malicious actor is altering files, and won't appear in regular usage.

At a glance

Exploitability

Can be exploited over the network without logging in, but needs a user to act. High risk of service disruption.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-20 16:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-24 20:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 5.9 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-07-20 16:16 UTC

Last modified

2026-10-24 20:10 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-125 · Out-of-bounds read

Record status

Analyzed

Affected

• Hdfgroup hdf5 < 2.1.0

Attack profile CVSS 4.0 · 5.9

Attack vector

Network

Complexity

High

Attack requirements

Present

Privileges needed

None

User interaction

Active

Confidentiality

None

Integrity

None

Availability

High

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-26197.md and follow it. Check whether this project is affected by CVE-2026-26197. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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