In the Linux kernel, the following vulnerability has been resolved:
usb: cdc-acm: Check control transfer buffer size before access
If the first fragment is shorter than struct usb_cdc_notification, we can't
calculate an expected_size. Log an error and discard the notification
instead of reading lengths from memory outside the received data, which can
lead to memory corruption when the expected_size decreases between
fragments, causing expected_size - acm->nb_index to wrap.
This issue has been present since the beginning of git history; however,
it only leads to memory corruption since commit ea2583529cd1
("cdc-acm: reassemble fragmented notifications").
A mitigating factor is that acm_ctrl_irq() can only execute after userspace
has opened /dev/ttyACM*; but if ModemManager is running, ModemManager will
do that automatically depending on the USB device's vendor/product IDs and
its other interfaces.
| Score | Percentile |
|---|---|
| 0.03% | 6.96% |
| Base score | Version | Severity | Vector |
|---|---|---|---|
| 7.8 | 3.1 | — |
|
| Type | Value |
|---|---|
| GHSA | GHSA-48g3-w2gf-xjrv ↗ |
| CVE | CVE-2025-21704 ↗ |
| CWE id | Name |
|---|---|
| CWE-787 | Out-of-bounds Write |