CVE-2022-49940 tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf()
A null pointer dereference in the Linux kernel's n_gsm driver allows local attackers to cause a system crash via ioctl calls.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2022-49940?
CVE-2022-49940 is a medium-severity vulnerability in Linux kernel, published on 18 Jun 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
tty: n_gsm: add sanity check for gsm->receive in gsm_receive_buf()
A null pointer dereference can happen when attempting to access the "gsm->receive()" function in gsmld_receive_buf(). Currently, the code assumes that gsm->recieve is only called after MUX activation. Since the gsmld_receive_buf() function can be accessed without the need to initialize the MUX, the gsm->receive() function will not be set and a NULL pointer dereference will occur.
Fix this by avoiding the call to "gsm->receive()" in case the function is not initialized by adding a sanity check.
Call Trace: <TASK> gsmld_receive_buf+0x1c2/0x2f0 drivers/tty/n_gsm.c:2861 tiocsti drivers/tty/tty_io.c:2293 [inline] tty_ioctl+0xa75/0x15d0 drivers/tty/tty_io.c:2692 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:870 [inline] __se_sys_ioctl fs/ioctl.c:856 [inline] __x64_sys_ioctl+0x193/0x200 fs/ioctl.c:856 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x35/0xb0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
Weakness: CWE-476
Which versions are affected by CVE-2022-49940?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2022-49940?
Apply the vendor's patch.
Is CVE-2022-49940 being exploited?
There is no known exploitation of CVE-2022-49940 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as DEBIAN-CVE-2022-49940, GHSA-52j6-g7fj-mfjm, ROOT-OS-UBUNTU-2204-CVE-2022-49940, ROOT-OS-UBUNTU-2404-CVE-2022-49940, UBUNTU-CVE-2022-49940.