CVE-2026-23181

/// Technical description

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

btrfs: sync read disk super and set block size

When the user performs a btrfs mount, the block device is not set

correctly. The user sets the block size of the block device to 0x4000

by executing the BLKBSZSET command.

Since the block size change also changes the mapping->flags value, this

further affects the result of the mapping_min_folio_order() calculation.

Let's analyze the following two scenarios:

Scenario 1: Without executing the BLKBSZSET command, the block size is

0x1000, and mapping_min_folio_order() returns 0;

Scenario 2: After executing the BLKBSZSET command, the block size is

0x4000, and mapping_min_folio_order() returns 2.

do_read_cache_folio() allocates a folio before the BLKBSZSET command

is executed. This results in the allocated folio having an order value

of 0. Later, after BLKBSZSET is executed, the block size increases to

0x4000, and the mapping_min_folio_order() calculation result becomes 2.

/// 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