---
id: CVE-2026-89738
title: 'usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed'
summary: |-
  In the Linux kernel, the following vulnerability has been resolved:

  usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

  In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a
  self-restarting cycle: …
severity: high
cvss: 7.8
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H'
cvssSource: cna
cwe:
  - CWE-825
vendor: Linux
product: Linux
affected:
  - >-
    Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 <
    723d73b245843d4fff4c3f42e857c78c2b2d414e
  - >-
    Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 <
    a2a602cb1e28d76a5398cec3fa21b0110385f501
  - >-
    Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 <
    51a311eb97e91ce1aed3005cb71ccb2e30f8cce8
  - >-
    Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 <
    557ef547d49ff5e6026a4d39bdd3113bd81d7688
  - >-
    Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 <
    c27d13ce4bab80fbdf6523928071b6c24b37606c
  - Linux 2.6.36
published: '2026-09-11'
updated: '2026-10-21'
sourceUpdated: '2026-10-21T12:48:31.419Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-89738'
references:
  - url: 'https://git.kernel.org/stable/c/723d73b245843d4fff4c3f42e857c78c2b2d414e'
  - url: 'https://git.kernel.org/stable/c/a2a602cb1e28d76a5398cec3fa21b0110385f501'
  - url: 'https://git.kernel.org/stable/c/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8'
  - url: 'https://git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688'
  - url: 'https://git.kernel.org/stable/c/c27d13ce4bab80fbdf6523928071b6c24b37606c'
  - url: >-
      https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89738.json
  - url: 'https://access.redhat.com/security/cve/CVE-2026-89738'
  - url: 'https://bugzilla.redhat.com/show_bug.cgi?id=2532232'
  - url: 'https://www.cve.org/CVERecord?id=CVE-2026-89738'
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-89738'
  - url: >-
      https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-89738.mbox
tags:
  - cve.org
  - csaf
  - vex
  - red-hat
  - score-dispute
epss: 0.00192
epssPercentile: 0.08744
scores:
  cna: 7.8
  vendor: 5.5
ingestedAt: '2026-09-14T15:23:07.472Z'
---

## Overview

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

usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed

In polled-VBUS mode (board.vbus_pin && board.vbus_polled), probe arms a
self-restarting cycle: at91_vbus_timer() schedules vbus_timer_work, and
at91_vbus_timer_work() calls at91_vbus_update() and re-arms the timer via
mod_timer(). Both recover the same udc through container_of and dereference
it on every iteration.

Neither teardown path cancels this cycle. udc is devm-allocated, so it is
freed after at91udc_remove() returns, and is likewise freed when probe
fails and devres runs. A timer callback or work item that is pending or
running at either point dereferences the freed udc.

Add at91_udc_shutdown_vbus_timer() and call it from at91udc_remove() and
from the usb_add_gadget_udc() failure path in probe; the remaining probe
error paths fail before the timer is armed. timer_shutdown_sync() waits
for a running callback and clears timer->function, which makes the work
handler's mod_timer() a permanent no-op; cancel_work_sync() then drains
any pending or running work whose re-arm attempt now does nothing. The
timer must be shut down first, since cancelling the work alone would let
the timer re-queue it. The guard mirrors probe: in IRQ mode the timer and
work_struct are never initialized.

This does not require a fault; a normal driver unbind can interleave with
an already queued work item.

This issue was found by an in-house static analysis tool.

## Affected

- `Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 < 723d73b245843d4fff4c3f42e857c78c2b2d414e`
- `Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 < a2a602cb1e28d76a5398cec3fa21b0110385f501`
- `Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 < 51a311eb97e91ce1aed3005cb71ccb2e30f8cce8`
- `Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 < 557ef547d49ff5e6026a4d39bdd3113bd81d7688`
- `Linux >= 4037242c4f5ff77afe61bf07ca1e8a99490219e5 < c27d13ce4bab80fbdf6523928071b6c24b37606c`
- `Linux 2.6.36`

## Remediation

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

## Vendor advisories

- **Red Hat VEX** · Moderate · updated 2026-09-21 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-89738.json)