CVE-2026-43359

/// Technical description

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

btrfs: fix transaction abort on set received ioctl due to item overflow

If the set received ioctl fails due to an item overflow when attempting to

add the BTRFS_UUID_KEY_RECEIVED_SUBVOL we have to abort the transaction

since we did some metadata updates before.

This means that if a user calls this ioctl with the same received UUID

field for a lot of subvolumes, we will hit the overflow, trigger the

transaction abort and turn the filesystem into RO mode. A malicious user

could exploit this, and this ioctl does not even requires that a user

has admin privileges (CAP_SYS_ADMIN), only that he/she owns the subvolume.

Fix this by doing an early check for item overflow before starting a

transaction. This is also race safe because we are holding the subvol_sem

semaphore in exclusive (write) mode.

A test case for fstests will follow soon.

/// 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