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Fencer Vulns
medium 5.5

CVE-2021-38203 json

btrfs in the Linux kernel before 5.13.4 allows attackers to cause a denial of service (deadlock) via processes that trigger allocation of n…

published 2021-08-08 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-24661

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 30%
public exploits
0
none known

Summary

btrfs in the Linux kernel before 5.13.4 allows attackers to cause a denial of service (deadlock) via processes that trigger allocation of new system chunks during times when there is a shortage of free space in the system space_info.

Patch / fix

  • linux linux_kernel 5.13.4
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-38203

  • linux-oem-5.13 Ubuntu 20.04 LTS 5.13.0-1014.18

ubuntu advisories UBUNTU-CVE-2021-38203

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

  • kernel CBL-Mariner 2.0 5.10.78.1-1

azure linux advisories AZL-6587

Azure Linux vulnerability data, Copyright (c) Microsoft Corporation, from https://github.com/microsoft/AzureLinuxVulnerabilityData via OSV, under the MIT licence; changed: normalised to fixed package versions per release. MIT

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2021-38203 updated cvss 5.5

kernel: btrfs: deadlock via processes that trigger allocation of new system chunks during times when there is a shortage of free space in the system space_info

  • Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, kernel-alt, python-perf, +9 more Red Hat Enterprise Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +82 more
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.36% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/torvalds/linux/commit/1cb3db1cf383a3c7dbda1aa0ce748b0958759947 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.5 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
NVD 2.0 2.1 AV:L/AC:L/Au:N/C:N/I:N/A:P

Classification

Weakness
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.