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CVE-2026-26199 HDFGroup CVE debrief

The HDF5 library is vulnerable to an underflow issue when invoking `H5Iget_name` with a group id and a size parameter of 0. This can occur if `H5Iget_name` is invoked in a way where `size` can be forced to zero, and there is important data before the `name` buffer. The vulnerability has a CVSS score of 5.9 and is classified as MEDIUM severity. Users of the HDF5 library should be aware of this vulnerability and take steps to mitigate it. The CVE record was published on 2026-07-20T16:16:57.550Z and has not been modified since then.

Vendor
HDFGroup
Product
hdf5
CVSS
MEDIUM 5.9
CISA KEV
Not listed in stored evidence
Original CVE published
2026-07-20
Original CVE updated
2026-07-20
Advisory published
2026-07-20
Advisory updated
2026-07-20

Who should care

Users of the HDF5 library, particularly those who use it in their applications, should be aware of this vulnerability and take steps to mitigate it. This includes updating to the latest version of the HDF5 library and using safe coding practices when invoking `H5Iget_name`. Additionally, users should review their systems and applications for potential exposure and take steps to protect themselves.

Technical summary

The HDF5 library has a vulnerability in the `H5Iget_name` function. When invoked with a group id and a size parameter of 0, it can underflow when trying to place a null terminator in the buffer. This can occur if `H5Iget_name` is invoked in a way where `size` can be forced to zero, and there is important data before the `name` buffer. The vulnerability has a CVSS score of 5.9 and is classified as MEDIUM severity.

Defensive priority

Medium

Recommended defensive actions

  • Update to the latest version of the HDF5 library
  • Use safe coding practices when invoking `H5Iget_name`
  • Monitor for potential exploitation attempts
  • Review compensating controls for exposed systems while remediation is scheduled and verified
  • Check relevant monitoring, detection, and logs for exposed assets that need extra review
  • Track exceptions, retest remediated assets, and close the item only after evidence is documented
  • Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record was published on 2026-07-20T16:16:57.550Z and was last modified on 2026-07-20T19:17:20.487Z. The NVD entry is currently Unverified. The HDF5 library's vulnerability in `H5Iget_name` function can be triggered if the function is invoked with a group id and a size parameter of 0, potentially leading to underflow. This can occur if `H5Iget_name` is invoked in a way where `size` can be forced to zero, and there is important data before the `name` buffer. Evidence limits suggest that further verification is needed to confirm affected scope and severity.

Official resources

AI-assisted PatchSiren debrief based on the supplied source corpus. The CVE record was published on 2026-07-20T16:16:57.550Z and has not been modified since then. The NVD entry is currently Unverified.