CVE-2026-45851

/// Technical description

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

efi: Fix reservation of unaccepted memory table

The reserve_unaccepted() function incorrectly calculates the size of the

memblock reservation for the unaccepted memory table. It aligns the

size of the table, but fails to account for cases where the table's

starting physical address (efi.unaccepted) is not page-aligned.

If the table starts at an offset within a page and its end crosses into

a subsequent page that the aligned size does not cover, the end of the

table will not be reserved. This can lead to the table being overwritten

or inaccessible, causing a kernel panic in accept_memory().

This issue was observed when starting Intel TDX VMs with specific memory

sizes (e.g., > 64GB).

Fix this by calculating the end address first (including the unaligned

start) and then aligning it up, ensuring the entire range is covered

by the reservation.

/// 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