CVE-2026-72338

/// Technical description

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

net/sched: act_pedit: fix TOCTOU heap OOB write in tc offload

There is a TOCTOU race condition in flower lockless approach between sizing

a flow_rule buffer and filling it.

[email protected] reports:

The cls_flower classifier operates with TCF_PROTO_OPS_DOIT_UNLOCKED

(fl_change runs without RTNL), while RTM_NEWACTION holds RTNL, so the

independent locking domains make the race reachable in practice. KASAN

confirms:

BUG: KASAN: slab-out-of-bounds in tcf_pedit_offload_act_setup+0x81b/0x930

Write of size 4 at addr ffff888001f27520 by task poc-toctou/312

The buggy address is located 0 bytes to the right of

allocated 288-byte region [ffff888001f27400, ffff888001f27520)

(cache kmalloc-512)

Note: The result is a heap OOB write attacker-controlled content into the

adjacent slab object (requires CAP_NET_ADMIN).

The fix introduces reading tcfp_nkeys under act->tcfa_lock in all places

using a new tcf

/// 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