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Fencer Vulns
medium 6.8

CVE-2026-19028 json

HDF5 integer underflow in Fletcher32 filter leads to massive out-of-bounds read

published 2026-08-05 3 mo ago modified 2026-10-23 16 d ago also EUVD-2026-53676

cvss
6.8
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.2%
EPSS 0.2% chance of exploitation in 30 days, percentile 9%
public exploits
0
none known

Summary

H5Z__filter_fletcher32 in H5Zfletcher32.c in HDF5 prior to 2.3.0 computes the data length to checksum by subtracting the 4-byte trailing checksum size from the input buffer size without checking that the buffer is at least 4 bytes, allowing a size_t underflow. This allows attackers to cause a denial of service (massively out-of-bounds read and application crash in H5_checksum_fletcher32) via a crafted HDF5 file with a Fletcher32-filtered chunk smaller than 4 bytes, triggered via H5Dread, e.g. by the h5ls or h5dump tools.

Patch / fix

  • hdf5 hummingbird 1 2.2.0-0.1.2.hum1
  • java-hdf5 hummingbird 1 2.2.0-0.1.2.hum1
  • hdf5-mpich hummingbird 1 2.2.0-0.1.2.hum1
  • hdf5-openmpi hummingbird 1 2.2.0-0.1.2.hum1

red hat advisories RHSA-2026:73539

  • hdf5 Azure Linux 3.0 1.14.6-6

azure linux advisories AZL-94499

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-19028 updated cvss 5.5

hdf5: HDF5: Denial of Service via integer underflow in Fletcher32 filter

  • Red Hat Enterprise Linux AI (RHEL AI) 3 hdf5
    affected: workaround, no fix available
  • Red Hat Hardened Images hdf5 2.2.0-0.1.2.hum1, java-hdf5 2.2.0-0.1.2.hum1, hdf5-mpich 2.2.0-0.1.2.hum1, hdf5-openmpi 2.2.0-0.1.2.hum1
    fixed: vendor fix RHSA-2026:73539

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.19% chance of exploitation in the next 30 days, higher than 9% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/HDFGroup/hdf5/issues/6488 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 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
CNA 4.0 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • The HDF Group HDF5

Classification

Weakness
  • CWE-190 Integer Overflow or Wraparound
  • CWE-125 Out-of-bounds Read
  • CWE-1284 Improper Validation of Specified Quantity in Input

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.