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Fencer Vulns
medium 5.5

CVE-2021-20265 json

A flaw was found in the way memory resources were freed in the unix_stream_recvmsg function in the Linux kernel when a signal was pending.

published 2021-03-10 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-7701

cvss
5.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits
0
none known

Summary

A flaw was found in the way memory resources were freed in the unix_stream_recvmsg function in the Linux kernel when a signal was pending. This flaw allows an unprivileged local user to crash the system by exhausting available memory. The highest threat from this vulnerability is to system availability.

Patch / fix

  • linux Debian 14, Debian 13, Debian 12 4.4.4-1

debian advisories DEBIAN-CVE-2021-20265

  • linux-raspi2 Ubuntu 16.04 LTS 4.4.0-1010.13

ubuntu advisories UBUNTU-CVE-2021-20265

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 RHEL 7 3.10.0-1160.21.1.el7
  • perf RHEL 7 3.10.0-1160.21.1.el7
  • bpftool RHEL 7 3.10.0-1160.21.1.el7
  • python-perf RHEL 7 3.10.0-1160.21.1.el7
  • kernel-kdump RHEL 7 3.10.0-1160.21.1.el7
  • kernel-tools RHEL 7 3.10.0-1160.21.1.el7
  • kernel-tools-libs RHEL 7 3.10.0-1160.21.1.el7
  • kernel-bootwrapper RHEL 7 3.10.0-1160.21.1.el7

red hat advisories RHSA-2021:1288RHSA-2021:0856RHSA-2021:0857

  • kernel-syms SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 4.4.180-94.150.1
  • kernel-source SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +3 more 4.4.180-94.150.1
  • kernel-default SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 4.4.180-94.150.1
  • kgraft-patch-SLE12-SP3_Update_41 SLES for SAP 12 SP3, SLES 12 SP3-LTSS, OpenStack Cloud Crowbar 8 +2 more 1-4.3.1
  • kernel-syms SLES 12 SP2-BCL 4.4.121-92.161.1
  • kernel-source SLES 12 SP2-BCL 4.4.121-92.161.1
  • kernel-default SLES 12 SP2-BCL 4.4.121-92.161.1
  • kernel-ec2 SLES 11 SP4-LTSS 3.0.101-108.132.1

suse advisories SUSE-SU-2021:3935-1SUSE-SU-2021:3929-1SUSE-SU-2021:14849-1

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-2021-20265 updated cvss 5.1

kernel: increase slab leak leads to DoS

  • Red Hat Enterprise Linux Client (v. 7) perf 3.10.0-1160.21.1.el7, kernel 3.10.0-1160.21.1.el7, bpftool 3.10.0-1160.21.1.el7, python-perf 3.10.0-1160.21.1.el7, kernel-tools 3.10.0-1160.21.1.el7, kernel-tools-libs 3.10.0-1160.21.1.el7, +2 more Red Hat Enterprise Linux Client Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.21.1.el7 Red Hat Enterprise Linux ComputeNode Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.21.1.el7
    fixed: vendor fix RHSA-2021:0856
  • Red Hat Enterprise Linux for Real Time (v. 7) kernel-rt 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-trace 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.21.1.rt56.1158.el7 Red Hat Enterprise Linux for Real Time for NFV (v. 7) kernel-rt 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-kvm 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-trace 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-debug-kvm 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-trace-kvm 3.10.0-1160.21.1.rt56.1158.el7, kernel-rt-debuginfo-common-x86_64 3.10.0-1160.21.1.rt56.1158.el7
    fixed: vendor fix RHSA-2021:0857
  • Red Hat Enterprise Linux Server (v. 6 ELS) perf 2.6.32-754.39.1.el6, kernel 2.6.32-754.39.1.el6, kernel-kdump 2.6.32-754.39.1.el6, kernel-firmware 2.6.32-754.39.1.el6, kernel-abi-whitelists 2.6.32-754.39.1.el6, kernel-debuginfo-common-i686 2.6.32-754.39.1.el6, +2 more
    fixed: vendor fix RHSA-2021:1288
  • Red Hat Enterprise Linux Server (v. 7) perf 3.10.0-1160.21.1.el7, kernel 3.10.0-1160.21.1.el7, bpftool 3.10.0-1160.21.1.el7, python-perf 3.10.0-1160.21.1.el7, kernel-kdump 3.10.0-1160.21.1.el7, kernel-tools 3.10.0-1160.21.1.el7, +7 more
    fixed: vendor fix RHSA-2021:0856
  • Red Hat Enterprise Linux Server Optional (v. 6 ELS) python-perf 2.6.32-754.39.1.el6, kernel-debuginfo-common-i686 2.6.32-754.39.1.el6, kernel-debuginfo-common-s390x 2.6.32-754.39.1.el6, kernel-debuginfo-common-x86_64 2.6.32-754.39.1.el6
    fixed: vendor fix RHSA-2021:1288
  • Red Hat Enterprise Linux Server Optional (v. 7) kernel-debuginfo-common-ppc64 3.10.0-1160.21.1.el7, kernel-debuginfo-common-x86_64 3.10.0-1160.21.1.el7, kernel-debuginfo-common-ppc64le 3.10.0-1160.21.1.el7 Red Hat Enterprise Linux Workstation (v. 7) perf 3.10.0-1160.21.1.el7, kernel 3.10.0-1160.21.1.el7, bpftool 3.10.0-1160.21.1.el7, python-perf 3.10.0-1160.21.1.el7, kernel-tools 3.10.0-1160.21.1.el7, kernel-tools-libs 3.10.0-1160.21.1.el7, +2 more Red Hat Enterprise Linux Workstation Optional (v. 7) kernel-debuginfo-common-x86_64 3.10.0-1160.21.1.el7
    fixed: vendor fix RHSA-2021:0856
  • Red Hat Enterprise Linux 7 perf, kernel, kernel-alt, python-perf, kernel-kdump, kernel-tools, +3 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

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

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 4.9 AV:L/AC:L/Au:N/C:N/I:N/A:C

Affected products

  • n/a kernel

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption
  • CWE-401 Missing Release of Memory after Effective Lifetime
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.