---
cve: "CVE-2026-89738"
severity: "HIGH"
cvss: 7.8
epss: "16%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-09-11 20:20:04"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-19T10:45:21+02:00"
---

# CVE-2026-89738

> 7.8 HIGH

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.12.109
- Kernel ≥ 6.18.50
- Kernel ≥ 7.2.4

## Referenzen

- <https://git.kernel.org/stable/c/a2a602cb1e28d76a5398cec3fa21b0110385f501>
- <https://git.kernel.org/stable/c/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8>
- <https://git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688>
- <https://git.kernel.org/stable/c/c27d13ce4bab80fbdf6523928071b6c24b37606c>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-89738) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_