CVE-2025-38448: usb: gadget: u_serial: Fix race condition in TTY wakeup

Severity: medium (CVSS 4.7 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2025-07-25 · updated 2026-06-17
Weakness: CWE-362

Description

In the Linux kernel, the following vulnerability has been resolved: usb: gadget: u_serial: Fix race condition in TTY wakeup A race condition occurs when gs_start_io() calls either gs_start_rx() or gs_start_tx(), as those functions briefly drop the port_lock for usb_ep_queue(). This allows gs_close() and gserial_disconnect() to clear port.tty and port_usb, respectively. Use the null-safe TTY Port helper function to wake up TTY. Example CPU1: CPU2: gserial_connect() // lock gs_close() // await lock gs_start_rx() // unlock usb_ep_queue() gs_close() // lock, reset port.tty and unlock gs_start_rx() // lock tty_wakeup() // NPE

Affected products

Debian Linux: 11.0
Linux kernel: from 3.5 before 5.4.296; from 5.5 before 5.10.240; from 5.11 before 5.15.189; from 5.16 before 6.1.146; from 6.2 before 6.6.99; from 6.7 before 6.12.39 — fixed in 5.10.240, 5.15.189, 5.4.296, 6.1.146, 6.12.39, 6.15.7

How to fix

Upgrade to a fixed version: Linux kernel 5.10.240, 5.15.189, 5.4.296, 6.1.146. Check the vendor advisory for mitigations.

References

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