CVE-2021-4149 Denial of service in kernel

What is CVE-2021-4149?

CVE-2021-4149 is a medium-severity denial of service vulnerability in Debian Debian Linux, published on 23 Mar 2022. It can only be exploited from the same machine or local network, with no action from the victim.

Official 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.

Weakness: CWE-667

Which versions are affected by CVE-2021-4149?

It affects 2 products.

Products include Debian Debian Linux, Linux kernel.

How do I fix CVE-2021-4149?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2021-4149 being exploited?

There is no known exploitation of CVE-2021-4149 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

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• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-4149, GHSA-j26f-m94f-4hr4, UBUNTU-CVE-2021-4149.