What’s Vulnerable › Vulnerabilities

CVE-2026-19028: HDF5 integer underflow in Fletcher32 filter leads to massive out-of-bounds read

• Severity: medium (CVSS 6.8 v4.0)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-06 · updated 2026-10-23
• Weakness: CWE-125

Description

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.

Affected products

• HDF5: through 2.3.0

References

• https://github.com/HDFGroup/hdf5/issues/6488
• https://github.com/HDFGroup/hdf5/issues/6490
• https://github.com/HDFGroup/hdf5/pull/6497
• https://github.com/HDFGroup/hdf5/issues/6488

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