CVE-2026-53264

Technical Description

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

net/sched: act_api: use RCU with deferred freeing for action lifecycle

When NEWTFILTER and DELFILTER are run concurrently it is possible to create a

race with an associated action.

Let's illustrate with CPU0 running NEWTFILTER and CPU1 running DELFILTER:

0: mutex_lock() <-- holds the idr lock

0: rcu_read_lock()

0: p = idr_find(idr, index) <-- action p is valid (RCU protects IDR)

0: mutex_unlock() <-- releases the idr lock

1: refcount_dec_and_mutex_lock() <-- refcnt 1->0, mutex held

1: idr_remove(idr, index) <-- Action removed from IDR

1: mutex_unlock() <-- mutex released allowing us to delete the action

1: tcf_action_cleanup(p); kfree(p) <-- Kfrees p immediately, no deferral

0: refcount_inc_not_zero(&p->tcfa_refcnt) <-- ouch, UAF p points to freed memory

This patch fixes the race condition between NEWTFILTER and DELFILTER by

adding struct rcu_head to tc_action used in the deferral and introducing a

call_r

Remediation

Check the references section for vendor advisories and patches from linux. Update linux_kernel to the latest patched version. 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.

Affected Products

References