CVE-2025-40071

What the bug is

Currently gsm_queue() processes incoming frames and when opening a DLC channel it calls gsm_dlci_open() which calls gsm_modem_update(). If basic mode is used it calls gsm_modem_upd_via_msc() and it cannot block the input queue by waiting the response to come into the same input queue. Instead allow sending Modem Status Command without waiting for remote end to respond. Define a new function gsm_modem_send_initial_msc() for this purpose. As MSC is only valid for basic encoding, it does not do anything for advanced or when convergence layer type 2 is used.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

drivers/tty/n_gsm.c

What this is

TTY LAYER AND SERIAL DRIVERSMAINTAINERS section matched on drivers/tty/ · linux-kernel@vger.kernel.org · Supported

Kernel module

none to look for. The file would have gone into n_gsm, and Debian does not compile it into that module, so finding n_gsm in lsmod would say nothing about this CVE.

Check it on the machine

grep -w CONFIG_N_GSM /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code. In 4 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.

• bookworm, trixie, forky, sidn

n

not enabled on any flavour - this release does not build the code

Build switch

CONFIG_N_GSM

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2025-10-28 (12 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.20%, higher than 9.3% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

drivers/tty

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
5.18	6.6.112	c36785f9de03
5.18	6.12.53	5416e89b81b0
5.18	6.17.3	c5a2791a7f11
5.18	6.18	3cf0b3c243e5
5.15.54	0	0
5.17.6	0	0