---
id: CVE-2026-72493
title: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: serialize netif_running() check in enqueue_to_backlog()

  Syzbot reported a KASAN slab-use-after-free in fib_rules_lookup().

  The root cause is a race condition whe…
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: serialize netif_running() check in enqueue_to_backlog()

  Syzbot reported a KASAN slab-use-after-free in fib_rules_lookup().

  The root cause is a race condition whe…
severity: critical
cvss: 9.9
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H'
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= e9e4dd3267d0c5234c5c0f47440456b10875dec9 <
    b422e3eff0edf0975de4883929adbed28f9d08bc
  - >-
    Linux >= e9e4dd3267d0c5234c5c0f47440456b10875dec9 <
    2fface6e0bbd6314d1d9d071abf2c4d67548511c
  - >-
    Linux >= e9e4dd3267d0c5234c5c0f47440456b10875dec9 <
    46762cefe7f4e5bffc1eb467810a7bbb02e461d7
  - Linux 78b6803a1961369d0b8350ff1f99b7375bbd7a8f
  - Linux b5d73d9cdd6be22795499890ea928a6f57ef829c
  - Linux f6533fed1bfa842e391ee50f9a9c5e963c71e579
  - Linux 2095ab2456da766174cda8bc105d7a7b1bc70e16
  - Linux f1fdb184aefa8447560e3ea0e605171592ffee41
  - Linux f75c8a3015422128ca150e81c730bc2a471b5f4a
  - Linux >= 3.2.71 < 3.3
  - Linux >= 3.4.111 < 3.5
  - Linux >= 3.12.48 < 3.13
  - Linux >= 3.14.54 < 3.15
  - Linux >= 3.18.22 < 3.19
  - Linux >= 4.1.9 < 4.2
  - Linux 4.2
published: '2026-08-15'
updated: '2026-10-15'
sourceUpdated: '2026-10-15T11:17:44.190'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-72493'
references:
  - url: 'https://git.kernel.org/stable/c/2fface6e0bbd6314d1d9d071abf2c4d67548511c'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/46762cefe7f4e5bffc1eb467810a7bbb02e461d7'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
  - url: 'https://git.kernel.org/stable/c/b422e3eff0edf0975de4883929adbed28f9d08bc'
    label: 416baaa9-dc9f-4396-8d5f-8c081fb06d67
tags:
  - nvd
  - cve.org
epss: 0.00348
epssPercentile: 0.2675
ingestedAt: '2026-10-15T11:00:41.680Z'
---

## Overview

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

net: serialize netif_running() check in enqueue_to_backlog()

Syzbot reported a KASAN slab-use-after-free in fib_rules_lookup().

The root cause is a race condition where packets can escape the backlog
flushing during device unregistration (e.g., during netns exit).

Commit e9e4dd3267d0 ("net: do not process device backlog during unregistration")
introduced a lockless netif_running() check in enqueue_to_backlog() to
prevent queuing packets to an unregistering device.

However, this creates a TOCTOU race window.

A lockless transmitter (like veth_xmit) can pass
the check before dev_close() clears IFF_UP. If the transmitter is then
delayed, flush_all_backlogs() can run and finish before the transmitter
grabs the backlog lock and queues the packet. The packet then escapes
the flush and triggers UAF later when processed.

Fix this by moving the netif_running() check inside the backlog lock.
This serializes the check with the flush work (which also grabs the lock).
We then either queue the packet before the flush runs (so it gets flushed),
or check netif_running() after the flush/close completes (so it gets dropped).

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.