---
id: CVE-2026-98773
title: 'USB: cdc-acm: skip URB restart in port_shutdown if disconnected'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  USB: cdc-acm: skip URB restart in port_shutdown if disconnected

  acm_port_shutdown() is called from the tty-port machinery whenever the
  last user closes the port.  acm_…
severity: none
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 603d5a7110832e10165d21f9a1486399457177de <
    9742905d9ed5bf23ebe4c100dec80b6bc50fb522
  - >-
    Linux >= 5d29d7ff8679e5a525f22da467ba33c042e8029b <
    a0ed07b5bbb2d8fcef86810453216070691816e7
  - >-
    Linux >= f58752ebcb35e156c85cd1a82d6579c7af3b9023 <
    420ca35af891d33522cc08504768ccd60a4c450a
  - >-
    Linux >= f58752ebcb35e156c85cd1a82d6579c7af3b9023 <
    dc614d6bc991740d41d5a99ac7765c4b675dda88
  - Linux d826061aa64cb28089bf4c73e301dd7928662b84
  - Linux 8fb82e3555a7d56a05d8ef0edee9859f889c0860
  - Linux 283f8162cc3c82086537cbc7dc01870dbeb07a91
  - Linux f77f10bc76c2da86b4248269472f6d971e37828b
  - Linux >= 6.12.83 < 6.12.113
  - Linux >= 6.18.24 < 6.18.56
  - Linux >= 6.1.175 < 6.2
  - Linux >= 6.6.136 < 6.7
  - Linux >= 6.19.14 < 6.20
  - Linux >= 7.0.1 < 7.1
  - Linux 7.1
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T15:48:09.093Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-98773'
references:
  - url: 'https://git.kernel.org/stable/c/9742905d9ed5bf23ebe4c100dec80b6bc50fb522'
  - url: 'https://git.kernel.org/stable/c/a0ed07b5bbb2d8fcef86810453216070691816e7'
  - url: 'https://git.kernel.org/stable/c/420ca35af891d33522cc08504768ccd60a4c450a'
  - url: 'https://git.kernel.org/stable/c/dc614d6bc991740d41d5a99ac7765c4b675dda88'
tags:
  - cve.org
ingestedAt: '2026-10-18T16:47:32.491Z'
---

## Overview

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

USB: cdc-acm: skip URB restart in port_shutdown if disconnected

acm_port_shutdown() is called from the tty-port machinery whenever the
last user closes the port.  acm_disconnect() sets acm->disconnected and
calls tty_port_tty_vhangup(), which eventually triggers port_shutdown().
At that point acm_disconnect() has already called acm_poison_urbs() and
is about to free the control and read URBs.

However, acm_port_shutdown() unconditionally calls acm_unpoison_urbs()
and, when the ALWAYS_POLL_CTRL quirk is set, immediately re-submits the
ctrlurb and all read URBs.  If the concurrent acm_disconnect() then
frees those URBs and their DMA buffers while they are in-flight, the
result is a use-after-free in acm_ctrl_irq() or acm_read_bulk_callback()
accessing the freed DMA memory.

Fix by checking acm->disconnected after draining the delayed anchor and
returning early: if we are in a disconnect path the URBs must remain
poisoned and must not be resubmitted.

The early return is placed after the delayed-anchor drain loop because
that loop only cancels write-side accounting (wb->use = false and
autopm counter) and does not touch the hardware path.

## Affected

- `Linux >= 603d5a7110832e10165d21f9a1486399457177de < 9742905d9ed5bf23ebe4c100dec80b6bc50fb522`
- `Linux >= 5d29d7ff8679e5a525f22da467ba33c042e8029b < a0ed07b5bbb2d8fcef86810453216070691816e7`
- `Linux >= f58752ebcb35e156c85cd1a82d6579c7af3b9023 < 420ca35af891d33522cc08504768ccd60a4c450a`
- `Linux >= f58752ebcb35e156c85cd1a82d6579c7af3b9023 < dc614d6bc991740d41d5a99ac7765c4b675dda88`
- `Linux d826061aa64cb28089bf4c73e301dd7928662b84`
- `Linux 8fb82e3555a7d56a05d8ef0edee9859f889c0860`
- `Linux 283f8162cc3c82086537cbc7dc01870dbeb07a91`
- `Linux f77f10bc76c2da86b4248269472f6d971e37828b`
- `Linux >= 6.12.83 < 6.12.113`
- `Linux >= 6.18.24 < 6.18.56`
- `Linux >= 6.1.175 < 6.2`
- `Linux >= 6.6.136 < 6.7`
- `Linux >= 6.19.14 < 6.20`
- `Linux >= 7.0.1 < 7.1`
- `Linux 7.1`

## Remediation

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