CVE-2025-39904

/// Technical description

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

arm64: kexec: initialize kexec_buf struct in load_other_segments()

Patch series "kexec: Fix invalid field access".

The kexec_buf structure was previously declared without initialization.

commit bf454ec31add ("kexec_file: allow to place kexec_buf randomly")

added a field that is always read but not consistently populated by all

architectures. This un-initialized field will contain garbage.

This is also triggering a UBSAN warning when the uninitialized data was

accessed:

------------[ cut here ]------------

UBSAN: invalid-load in ./include/linux/kexec.h:210:10

load of value 252 is not a valid value for type '_Bool'

Zero-initializing kexec_buf at declaration ensures all fields are cleanly

set, preventing future instances of uninitialized memory being used.

An initial fix was already landed for arm64[0], and this patchset fixes

the problem on the remaining arm64 code and on riscv, as raised by Mark.

Discussion

/// 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