---
id: CVE-2026-23436
title: 'net: shaper: protect from late creation of hierarchy'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  net: shaper: protect from late creation of hierarchy

  We look up a netdev during prep of Netlink ops (pre- callbacks)
  and take a ref to it. Then later in the body of th…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 93954b40f6a4fc43226c01a15b02732f884500f1 <
    719f6784f918f9e32f3ff3b197f900e852223f9d
  - >-
    Linux >= 93954b40f6a4fc43226c01a15b02732f884500f1 <
    d22921727023e7852704965e935f4d1fc83a5ec9
  - >-
    Linux >= 93954b40f6a4fc43226c01a15b02732f884500f1 <
    d75ec7e8ba1979a1eb0b9211d94d749cdce849c8
  - Linux 6.13
ssvc:
  exploitation: none
  automatable: 'no'
  technicalImpact: partial
  timestamp: '2026-11-05T21:30:39.794432Z'
published: '2026-04-03'
updated: '2026-11-05'
sourceUpdated: '2026-11-05T21:33:46.717Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-23436'
references:
  - url: 'https://git.kernel.org/stable/c/719f6784f918f9e32f3ff3b197f900e852223f9d'
  - url: 'https://git.kernel.org/stable/c/d22921727023e7852704965e935f4d1fc83a5ec9'
  - url: 'https://git.kernel.org/stable/c/d75ec7e8ba1979a1eb0b9211d94d749cdce849c8'
tags:
  - cve.org
epss: 0.00125
epssPercentile: 0.02249
ingestedAt: '2026-11-05T22:38:32.132Z'
---

## Overview

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

net: shaper: protect from late creation of hierarchy

We look up a netdev during prep of Netlink ops (pre- callbacks)
and take a ref to it. Then later in the body of the callback
we take its lock or RCU which are the actual protections.

The netdev may get unregistered in between the time we take
the ref and the time we lock it. We may allocate the hierarchy
after flush has already run, which would lead to a leak.

Take the instance lock in pre- already, this saves us from the race
and removes the need for dedicated lock/unlock callbacks completely.
After all, if there's any chance of write happening concurrently
with the flush - we're back to leaking the hierarchy.

We may take the lock for devices which don't support shapers but
we're only dealing with SET operations here, not taking the lock
would be optimizing for an error case.

## Affected

- `Linux >= 93954b40f6a4fc43226c01a15b02732f884500f1 < 719f6784f918f9e32f3ff3b197f900e852223f9d`
- `Linux >= 93954b40f6a4fc43226c01a15b02732f884500f1 < d22921727023e7852704965e935f4d1fc83a5ec9`
- `Linux >= 93954b40f6a4fc43226c01a15b02732f884500f1 < d75ec7e8ba1979a1eb0b9211d94d749cdce849c8`
- `Linux 6.13`

## Remediation

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