In the Linux kernel, the following vulnerability has been resolved:
usb: gadget: f_fs: Fix race between aio_cancel() and AIO request complete
FFS based applications can utilize the aio_cancel() callback to dequeue
pending USB requests submitted to the UDC. There is a scenario where the
FFS application issues an AIO cancel call, while the UDC is handling a
soft disconnect. For a DWC3 based implementation, the callstack looks
like the following:
DWC3 Gadget FFS Application
dwc3_gadget_soft_disconnect() ...
--> dwc3_stop_active_transfers()
--> dwc3_gadget_giveback(-ESHUTDOWN)
--> ffs_epfile_async_io_complete() ffs_aio_cancel()
--> usb_ep_free_request() --> usb_ep_dequeue()
There is currently no locking implemented between the AIO completion
handler and AIO cancel, so the issue occurs if the completion routine is
running in parallel to an AIO cancel call coming from the FFS application.
As the completion call frees the USB request (io_data->req) the FFS
application is also referencing it for the usb_ep_dequeue() call. This can
lead to accessing a stale/hanging pointer.
commit b566d38857fc ("usb: gadget: f_fs: use io_data->status consistently")
relocated the usb_ep_free_request() into ffs_epfile_async_io_complete().
However, in order to properly implement locking to mitigate this issue, the
spinlock can't be added to ffs_epfile_async_io_complete(), as
usb_ep_dequeue() (if successfully dequeuing a USB request) will call the
function driver's completion handler in the same context. Hence, leading
into a deadlock.
Fix this issue by moving the usb_ep_free_request() back to
ffs_user_copy_worker(), and ensuring that it explicitly sets io_data->req
to NULL after freeing it within the ffs->eps_lock. This resolves the race
condition above, as the ffs_aio_cancel() routine will not continue
attempting to dequeue a request that has already been freed, or the
ffs_user_copy_work() not freeing the USB request until the AIO cancel is
done referencing it.
This fix depends on
commit b566d38857fc ("usb: gadget: f_fs: use io_data->status
consistently")
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (5.6): severity, escalated by confirmed exploitation. This CVE's 5.6 is its impact severity (EG Severity), not escalated.
- EG Severity
- 5.6 MEDIUMCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-25). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at every mission impact level.CISA BOD 26-04: 60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at every mission impact level.
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)60 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it