# CVE-2026-19026: Nbit filter NULL/short parameter-array dereference

> Attackers can cause denial of service via crafted HDF5 files due to missing NULL checks in the Nbit filter.

- **Severity:** Medium 6.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 5 Aug 2026
- **Updated:** 6 Oct 2026
- **Also known as:** AZL-94502, DEBIAN-CVE-2026-19026, ECHO-5628-d076-3b4e, GHSA-fr64-5gr2-c3jj, UBUNTU-CVE-2026-19026

## What is CVE-2026-19026?

CVE-2026-19026 is a medium-severity vulnerability in The HDF Group HDF5, published on 5 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

H5Z__filter_nbit in H5Znbit.c in HDF5 prior to 2.3.0 dereferences cd_values[0] through cd_values[4] without validating that cd_values is non-NULL or that cd_nelmts is at least 5, the fixed size of the filter's header. This allows attackers to cause a denial of service via a crafted HDF5 file that stores the N-Bit filter pipeline message with zero client-data values, opened and read via H5Dread, e.g. by the h5ls or h5repack tools.

Weakness: CWE-476 (NULL Pointer Dereference), CWE-1284 (Improper Validation of Specified Quantity in Input)

## Which versions are affected by CVE-2026-19026?


## How do I fix CVE-2026-19026?

Upgrade to a fixed version.

## Is CVE-2026-19026 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19026 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-19026 and fix it if it is affected.

What it is: CVE-2026-19026 is a medium-severity vulnerability in The HDF Group HDF5, published on 5 Aug 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-19026 exists.

Affected product: The HDF Group HDF5. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-19026/ (Markdown: https://insights.sbomify.com/CVE-2026-19026/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-19026
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-19026
- OSV: https://osv.dev/vulnerability/CVE-2026-19026

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-19026/
Summaries are generated and may contain mistakes; the official description above is the record.