Medium [CVE-2026-19028] Denial of Service via integer underflow in Fletcher32 filter
This medium-severity Red Hat Linux advisory covers CVE-2026-19028 affecting Red Hat Enterprise Linux AI (RHEL AI) 3, Red Hat Hardened Images.
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Summary
H5Z__filter_fletcher32 in H5Zfletcher32.c in HDF5 through 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. A flaw was found in HDF5.
An attacker can craft a malicious HDF5 file with a specially designed Fletcher32-filtered chunk. When this file is processed, an integer underflow occurs due to insufficient size validation, leading to a massive out-of-bounds read.
An integer underflow vulnerability exists in HDF5's H5Z__filter_fletcher32() function within H5Zfletcher32.c. When reading dataset chunks via H5Dread(), the Fletcher32 filter subtracts a 4-byte checksum length from the buffer size without validating that the buffer is at least 4 bytes.
Red Hat severity: Moderate — CVSS 5.5 (CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H). Weakness: CWE-125.
Affected Red Hat products: Red Hat Enterprise Linux AI (RHEL AI) 3; Red Hat Hardened Images. Red Hat does not currently list a fixing RHSA for this CVE.
- 2.3.0
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Mitigation checklist
- Do not open or process untrusted HDF5 files from unverified sources using tools or services linked against the HDF5 library. Enforce file-ingestion boundaries or access controls to restrict automated parsing of untrusted datasets.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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