CVE-2026-64369

Technical Description

In the Linux kernel, the following vulnerability has been resolved:

s390: Revert support for DCACHE_WORD_ACCESS

load_unaligned_zeropad() reads eight bytes from unaligned addresses and may

cross page boundaries. It handles exceptions which may happen if reading

from the second page results in an exception.

For pages which are donated to the Ultravisor for secure execution purposes

the do_secure_storage_access() exception handler however does not handle

such exceptions correctly. Such an exception may result in an endless

exception loop which will never be resolved.

An attempt to fix this [1] turned out to be not sufficient. For now revert

load_unaligned_zeropad() until this problem has been resolved in a proper

way.

Note that the implementation of load_unaligned_zeropad() itself is

correct. The revert is just a temporary workaround until there is complete

fix for secure storage access exceptions.

[1] commit b00be77302d7 ("s390/mm: Add missing secure storage access fixups for donat

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References