PatchSiren cyber security CVE debrief

CVE-2026-34734 HDFGroup CVE debrief

CVE-2026-34734 is a high-severity vulnerability in HDF5, a data management software. A heap-use-after-free issue was found in the h5dump helper utility, which can be triggered by a malicious h5 file. The vulnerability has a CVSS score of 7.8 and is classified as HIGH. The issue was reported on April 9, 2026, and last modified on June 30, 2026. 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. Evidence from the NVD and GitHub security advisories indicates that an attacker can supply a malicious h5 file to trigger the vulnerability.

Vendor: HDFGroup
Product: hdf5
CVSS: HIGH 7.8
CISA KEV: Not listed in stored evidence
Original CVE published: 2026-04-09
Original CVE updated: 2026-07-15
Advisory published: 2026-04-09
Advisory updated: 2026-07-15

Who should care

Organizations using HDF5 version 1.14.1-2 or earlier should prioritize patching this vulnerability. The vulnerability can be exploited by a local attacker with no privileges required. Successful exploitation can lead to high impact on confidentiality, integrity, and availability.

Technical summary

The vulnerability is caused by a heap-use-after-free issue in the h5dump helper utility of HDF5. The issue arises when a malicious h5 file is supplied, triggering a use-after-free error in the H5T__conv_struct function. The original object was allocated by H5D__typeinfo_init_phase3 and freed by H5D__typeinfo_term. The CVSS vector is CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H, indicating a high severity vulnerability.

Defensive priority

Patching is strongly recommended. Organizations should update HDF5 to a version that fixes this vulnerability. In the absence of a patch, defenders can consider monitoring for suspicious activity related to h5dump and restricting access to untrusted h5 files.

Recommended defensive actions

Patch HDF5 to a version that fixes the vulnerability
Restrict access to untrusted h5 files
Monitor for suspicious activity related to h5dump
Implement compensating controls to detect and prevent exploitation
Perform thorough inventory checks to identify affected systems

Evidence notes

The vulnerability was reported by an unknown source and details are based on NVD and GitHub security advisories. The CVE record and NVD detail pages provide additional information on the vulnerability. However, due to limited evidence, the full scope of affected systems and potential impact is not clear.

Sources and references

Verified primary and authoritative sources

CVE-2026-34734 CVE Program record
Publisher, destination, and source semantics verified

URL: https://www.cve.org/CVERecord?id=CVE-2026-34734

CVE Program - Official CVE Program record with source-provided CVE metadata.
CVE-2026-34734 NVD vulnerability detail
Publisher, destination, and source semantics verified

URL: https://nvd.nist.gov/vuln/detail/CVE-2026-34734

NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Mitigation or vendor reference
Unverified legacy reference

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

[email protected] - Exploit, Vendor Advisory
Source reference
Unverified legacy reference

URL: https://access.redhat.com/security/cve/CVE-2026-34734

0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Source reference
Unverified legacy reference

URL: https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-34734.json

0b0ca135-0b70-47e7-9f44-1890c2a1c46c

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.