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Fencer Intel
medium 5.5

CVE-2021-4149 json

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.

published 4y ago modified 4mo ago also EUVD-2021-34017

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 34%
public exploits
0
none known

Summary

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.

Patch / fix

  • linux linux_kernel 5.15
  • linux Debian 14, Debian 13, Debian 12 5.14.16-1

debian advisories DEBIAN-CVE-2021-4149

  • linux Ubuntu 18.04 LTS 4.15.0-184.194
  • linux Ubuntu 20.04 LTS 5.4.0-92.103
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1133.143
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1061.64
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1059.63
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1057.60
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1010.11
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1119.123

ubuntu advisories UBUNTU-CVE-2021-4149

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-rt SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.78.1
  • kernel-syms SLES 12 SP2-BCL 4.4.121-92.164.1
  • kernel-source SLES 12 SP2-BCL 4.4.121-92.164.1
  • kernel-default SLES 12 SP2-BCL 4.4.121-92.164.1
  • kernel-syms SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.88.1

suse advisories SUSE-SU-2022:0555-1SUSE-SU-2022:0477-1SUSE-SU-2022:0371-1SUSE-SU-2022:0367-1SUSE-SU-2022:0366-1SUSE-SU-2022:0364-1

  • kernel-default openSUSE Leap 15.3 4.12.14-197.105.1
  • kernel-vanilla openSUSE Leap 15.3 4.12.14-197.105.1
  • kernel-kvmsmall openSUSE Leap 15.3 4.12.14-197.105.1
  • kernel-zfcpdump openSUSE Leap 15.3 4.12.14-197.105.1
  • dtb-aarch64 openSUSE Leap 15.3 5.3.18-150300.59.43.1
  • kernel-64kb openSUSE Leap 15.3 5.3.18-150300.59.43.1
  • kernel-syms openSUSE Leap 15.3 5.3.18-150300.59.43.1
  • kernel-obs-qa openSUSE Leap 15.3 5.3.18-150300.59.43.1

opensuse advisories openSUSE-SU-2022:0366-1openSUSE-SU-2022:0198-1openSUSE-SU-2022:0169-1

Is CVE-2021-4149 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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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-2021-4149 updated cvss 4.7

kernel: Improper lock operation in btrfs

  • 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, python-perf, kernel-kdump, +8 more
    affected: workaround, no fix planned “Out of support scope”
  • 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

cisa ICSA-23-075-01 updated cvss 5.5

Siemens SCALANCE, RUGGEDCOM Third-Party

  • Siemens RUGGEDCOM RM1224 LTE(4G) EU (6GK6108-4AM00-2BA2) <V7.2 Siemens RUGGEDCOM RM1224 LTE(4G) NAM (6GK6108-4AM00-2DA2) <V7.2 Siemens SCALANCE M804PB (6GK5804-0AP00-2AA2) <V7.2 Siemens SCALANCE M812-1 ADSL-Router (Annex A) (6GK5812-1AA00-2AA2) <V7.2 Siemens SCALANCE M812-1 ADSL-Router (Annex B) (6GK5812-1BA00-2AA2) <V7.2 Siemens SCALANCE M816-1 ADSL-Router (Annex A) (6GK5816-1AA00-2AA2) <V7.2
    +14 more products
    Siemens SCALANCE M816-1 ADSL-Router (Annex B) (6GK5816-1BA00-2AA2) <V7.2 Siemens SCALANCE M826-2 SHDSL-Router (6GK5826-2AB00-2AB2) <V7.2 Siemens SCALANCE M874-2 (6GK5874-2AA00-2AA2) <V7.2 Siemens SCALANCE M874-3 (6GK5874-3AA00-2AA2) <V7.2 Siemens SCALANCE M876-3 (EVDO) (6GK5876-3AA02-2BA2) <V7.2 Siemens SCALANCE M876-3 (ROK) (6GK5876-3AA02-2EA2) <V7.2 Siemens SCALANCE M876-4 (6GK5876-4AA10-2BA2) <V7.2 Siemens SCALANCE M876-4 (EU) (6GK5876-4AA00-2BA2) <V7.2 Siemens SCALANCE M876-4 (NAM) (6GK5876-4AA00-2DA2) <V7.2 Siemens SCALANCE MUM853-1 (EU) (6GK5853-2EA00-2DA1) <V7.2 Siemens SCALANCE MUM856-1 (EU) (6GK5856-2EA00-3DA1) <V7.2 Siemens SCALANCE MUM856-1 (RoW) (6GK5856-2EA00-3AA1) <V7.2 Siemens SCALANCE S615 (6GK5615-0AA00-2AA2) <V7.2 Siemens SCALANCE S615 EEC (6GK5615-0AA01-2AA2) <V7.2
    affected: fixed in V7.2 support.industry.siemens.com

Facts from CISA's republication of the vendor's own advisory (CSAF); the linked advisory is the authoritative source. CISA notification · csaf

Exploit prediction

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • lkml.org https://lkml.org/lkml/2021/10/18/885 referenced PoC, tagged "exploit" by a source, unverified
  • lkml.org https://lkml.org/lkml/2021/9/13/2565 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

Affected products

  • n/a kernel

Classification

Weakness
Technology feeds

References

Sources

Fencer Intel 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.