# CVE-2026-120499: h5io before 0.2.6 Arbitrary Code Execution via read_hdf5

Status: published. Published: 2026-11-05. Updated: 2026-11-05.

h5io before 0.2.6 contains a code injection vulnerability in read_hdf5() that allows attackers to execute arbitrary code by supplying a crafted HDF5 file. Attackers can store Python code in a node titled timezone, which _triage_read() passes to eval() with builtins reachable, name an arbitrary module in class or custom-object nodes that _import_class() imports, or place pickled objects in pd_dataframe or pd_series nodes that pandas deserializes on read.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: VulnCheck) — https://github.com/h5io/h5io/commit/afff1d61b31790f8c27e6c577bb7703eb1883ddd

## Affected products and versions

- h5io / h5io (h5io): ≥ 0.1.0; < 0.2.6 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 8.5 (high); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 7.8 (high); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation poc; automatable no; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-95, CWE-502

## Exploit evidence

- exploit: https://github.com/h5io/h5io/security/advisories/GHSA-vwvw-f6v4-w737 (ADP: CISA-ADP)

## References

- https://github.com/h5io/h5io/security/advisories/GHSA-vwvw-f6v4-w737 (CNA: VulnCheck; vendor-advisory)

- https://github.com/h5io/h5io/commit/afff1d61b31790f8c27e6c577bb7703eb1883ddd (CNA: VulnCheck; patch)

- https://github.com/h5io/h5io/releases/tag/h5io-0.2.6 (CNA: VulnCheck; release-notes)

- https://github.com/h5io/h5io/blob/h5io-0.2.5/h5io/_h5io.py#L601-L604 (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/h5io-before-0.2.6-arbitrary-code-execution-via-read-hdf5 (CNA: VulnCheck; third-party-advisory)

- https://github.com/h5io/h5io/security/advisories/GHSA-vwvw-f6v4-w737 (ADP: CISA-ADP; exploit)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-120499; retrieved 2026-11-05; source updated 2026-11-05

Revision: 064a41f63f4fe0488e3813be523b7343d0006c96ead1b9a67785dd0ec39143a1

Canonical: https://y2.dev/cve/CVE-2026-120499

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