# CVE-2026-34734: HDF5: H5T__conv_struct Use After Free

> An attacker can trigger a heap use-after-free in the h5dump utility by supplying a malicious HDF5 file, potentially leading to code execution or crashes.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **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:** 9 Apr 2026
- **Updated:** 15 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-34734, ECHO-4587-2d95-fba0, GHSA-w7v2-9cmr-pwwj, JLSEC-2026-354, UBUNTU-CVE-2026-34734

## What is CVE-2026-34734?

CVE-2026-34734 is a high-severity use after free vulnerability in Hdfgroup Hdf5, published on 9 Apr 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

HDF5 is software for managing data. In 1.14.1-2 and earlier, a heap-use-after-free was found in the h5dump helper utility. An attacker who can supply a malicious h5 file can trigger a heap use-after-free. The freed object is referenced in a memmove call from H5T__conv_struct. The original object was allocated by H5D__typeinfo_init_phase3 and freed by H5D__typeinfo_term.

Weakness: CWE-825 (Expired Pointer Dereference), CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-34734?

It affects 1 product.


Products: Hdfgroup Hdf5.

## How do I fix CVE-2026-34734?

Upgrade to a fixed version.

## Is CVE-2026-34734 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-34734 exists.

## Other vulnerabilities in Hdfgroup Hdf5

- [CVE-2024-32608](https://insights.sbomify.com/CVE-2024-32608/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-29157](https://insights.sbomify.com/CVE-2024-29157/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-29159](https://insights.sbomify.com/CVE-2024-29159/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-29164](https://insights.sbomify.com/CVE-2024-29164/): Memory corruption in n/a (critical 9.8)
- [CVE-2024-32611](https://insights.sbomify.com/CVE-2024-32611/): Other in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-34734 and fix it if it is affected.

What it is: CVE-2026-34734 is a high-severity use after free vulnerability in Hdfgroup Hdf5, published on 9 Apr 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-2026-34734 exists.

Affected product: Hdfgroup 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-2026-34734/ (Markdown: https://insights.sbomify.com/CVE-2026-34734/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34734
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34734
- OSV: https://osv.dev/vulnerability/CVE-2026-34734

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34734/
Summaries are generated and may contain mistakes; the official description above is the record.