CVE-2026-72338

Status: UPDATED  |  Advisory ID: CVE-2026-72338

Key Details

Affected Products, Subsystems & Sectors

What to Know

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_pedit_nkeys_locked() which replaces the old tcf_pedit_nkeys().

Additionally we close the remaining TOCTOU window between the sizing read and

the fill reads by more careful accounting.

Rather than silently truncating the key count, which leads to incorrect

action semantics offloaded to hardware and secondary OOB writes if

the remaining capacity is zero or consumed by prior actions, we enforce

remaining capacity checks and return -ENOSPC if the required space exceeds

the remaining capacity. (NVD)

What to Do

Monitor Linux's web page for any future patch releases.

References