CVE-2026-72338
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk6th percentile - higher than 6% of all known CVEs
Summary
In the Linux kernel's net/sched: act_pedit module, there is a TOCTOU vulnerability leading to a heap out-of-bounds write during TC offload. A race between sizing a flow_rule buffer and filling it can allow an attacker with CAP_NET_ADMIN to write controlled content beyond the allocated memory region.
Risk Assessment
The vulnerability allows a heap out-of-bounds write, which can lead to kernel memory corruption, system crashes, or potential privilege escalation. However, it requires CAP_NET_ADMIN, limiting risk to network administrators.
Recommendation
Apply the kernel patch that introduces reading tcfp_nkeys under act->tcfa_lock and enforces remaining capacity checks, returning -ENOSPC when exceeded. Also restrict access to CAP_NET_ADMIN.
Original NVD description (English source)
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.