CVE-2026-89648

/// Technical description

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

ceph: cap delegated inode count in ceph_parse_deleg_inos()

ceph_parse_deleg_inos() decodes interval sets of delegated inode numbers

from an MDS create-with-delegation reply. For each set it reads a 64-bit

start and a 64-bit len with ceph_decode_64_safe(), which only validates

that the eight bytes are present in the message, not the value, and then

loops over len while inserting entries into s_delegated_inos.

len is fully attacker controlled. A malicious or compromised MDS can send

one huge interval, many intervals in one reply, duplicate intervals, or

repeated replies that accumulate delegated inodes on the same session.

The original code bounded none of these and could spin the insert loop or

grow the xarray without limit.

Bound both dimensions with a single enforcement point. Track the number

of delegated inodes held by each MDS session in an atomic counter and

grow it only in ceph_insert_deleg_ino(), which uses

/// 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