High severity · published Sep 11, 2026
CVE-2026-89738
usb: gadget: at91_udc: drain polled-VBUS timer/work before udc is freed
7.8
CVSS
0.2%
EPSS
No
On KEV
Description
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 vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack vector
Local
Complexity
Low
Privileges
Low
User interaction
None
Confidentiality
High
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.2% · higher than 9% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
LI
Linux · Linux
4037242c4f5ff77afe61bf07ca1e8a99490219e5 before 723d73b245843d4fff4c3f42e857c78c2b2d414e; 4037242c4f5ff77afe61bf07ca1e8a99490219e5 before a2a602cb1e28d76a5398cec3fa21b0110385f501; 4037242c4f5ff77afe61bf07ca1e8a99490219e5 before 51a311eb97e91ce1aed3005cb71ccb2e30f8cce8; 4037242c4f5ff77afe61bf07ca1e8a99490219e5 before 557ef547d49ff5e6026a4d39bdd3113bd81d7688; 4037242c4f5ff77afe61bf07ca1e8a99490219e5 before c27d13ce4bab80fbdf6523928071b6c24b37606c; 2.6.36 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-89738
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-89738
git.kernel.org
https://git.kernel.org/stable/c/51a311eb97e91ce1aed3005cb71ccb2e30f8cce8
git.kernel.org
https://git.kernel.org/stable/c/557ef547d49ff5e6026a4d39bdd3113bd81d7688
git.kernel.org
https://git.kernel.org/stable/c/723d73b245843d4fff4c3f42e857c78c2b2d414e
git.kernel.org
https://git.kernel.org/stable/c/a2a602cb1e28d76a5398cec3fa21b0110385f501
git.kernel.org
https://git.kernel.org/stable/c/c27d13ce4bab80fbdf6523928071b6c24b37606c
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