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Fencer Vulns
low 3.5

CVE-2021-45486 json

In the IPv4 implementation in the Linux kernel before 5.12.4, net/ipv4/route.c has an information leak because the hash table is very small.

published 2021-12-25 4 y ago modified 2026-06-17 4 mo ago also EUVD-2021-32252

cvss
3.5
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

In the IPv4 implementation in the Linux kernel before 5.12.4, net/ipv4/route.c has an information leak because the hash table is very small.

Patch / fix

  • linux linux_kernel 5.12.4
  • linux Debian 14, Debian 13, Debian 12 5.10.38-1

debian advisories DEBIAN-CVE-2021-45486

  • linux Ubuntu 18.04 LTS 4.15.0-156.163
  • linux Ubuntu 20.04 LTS 5.4.0-77.86
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1111.118
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1051.53
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1046.49
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1046.48
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1099.101
  • linux-kvm Ubuntu 20.04 LTS 5.4.0-1041.42

ubuntu advisories UBUNTU-CVE-2021-45486

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 8 4.18.0-372.9.1.el8
  • perf RHEL 8 4.18.0-372.9.1.el8
  • bpftool RHEL 8 4.18.0-372.9.1.el8
  • kernel-core RHEL 8 4.18.0-372.9.1.el8
  • kernel-tools RHEL 8 4.18.0-372.9.1.el8
  • python3-perf RHEL 8 4.18.0-372.9.1.el8
  • kernel-modules RHEL 8 4.18.0-372.9.1.el8
  • kernel-zfcpdump RHEL 8 4.18.0-372.9.1.el8

red hat advisories RHSA-2022:1988RHSA-2022:6991RHSA-2022:6983RHSA-2022:1975

  • 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
  • kernel-source SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.88.1
  • kernel-default SLES for SAP 12 SP4, SLES 12 SP4-LTSS, SLE Live Patching 12 SP4 +3 more 4.12.14-95.88.1
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.83.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.83.1

suse advisories SUSE-SU-2022:0477-1SUSE-SU-2022:0371-1SUSE-SU-2022:0367-1SUSE-SU-2022:0366-1SUSE-SU-2022:0362-1SUSE-SU-2022:0289-1

  • 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-2022:0169-1openSUSE-SU-2022:0131-1openSUSE-SU-2022:0056-1

  • kernel AlmaLinux 8 4.18.0-372.9.1.el8
  • perf AlmaLinux 8 4.18.0-372.9.1.el8
  • bpftool AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-core AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-tools AlmaLinux 8 4.18.0-372.9.1.el8
  • python3-perf AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-modules AlmaLinux 8 4.18.0-372.9.1.el8
  • kernel-debug-core AlmaLinux 8 4.18.0-372.9.1.el8

almalinux advisories ALSA-2022:1988

  • kernel Rocky Linux 8 4.18.0-372.9.1.el8
  • kernel-rt Rocky Linux 8 4.18.0-372.9.1.rt7.166.el8

rocky linux advisories RLSA-2022:1988RLSA-2022:1975

  • kernel CBL-Mariner 2.0 5.15.2.1-1

azure linux advisories AZL-7098

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-2021-45486 updated cvss 3.5

kernel: information leak in the IPv4 implementation

  • 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 available
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-372.9.1.el8, kernel 4.18.0-372.9.1.el8, bpftool 4.18.0-372.9.1.el8, kernel-core 4.18.0-372.9.1.el8, kernel-tools 4.18.0-372.9.1.el8, python3-perf 4.18.0-372.9.1.el8, +15 more
    fixed: vendor fix RHSA-2022:1988
  • Red Hat Enterprise Linux BaseOS EUS (v.8.4) perf 4.18.0-305.65.1.el8_4, kernel 4.18.0-305.65.1.el8_4, bpftool 4.18.0-305.65.1.el8_4, kernel-core 4.18.0-305.65.1.el8_4, kernel-tools 4.18.0-305.65.1.el8_4, python3-perf 4.18.0-305.65.1.el8_4, +15 more
    fixed: vendor fix RHSA-2022:6983
  • Red Hat Enterprise Linux CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-372.9.1.el8, kernel-debuginfo-common-aarch64 4.18.0-372.9.1.el8, kernel-debuginfo-common-ppc64le 4.18.0-372.9.1.el8
    fixed: vendor fix RHSA-2022:1988
  • Red Hat Enterprise Linux CRB EUS (v.8.4) kernel-debuginfo-common-x86_64 4.18.0-305.65.1.el8_4, kernel-debuginfo-common-aarch64 4.18.0-305.65.1.el8_4, kernel-debuginfo-common-ppc64le 4.18.0-305.65.1.el8_4
    fixed: vendor fix RHSA-2022:6983
  • Red Hat Enterprise Linux NFV (v. 8) kernel-rt 4.18.0-372.9.1.rt7.166.el8, kernel-rt-kvm 4.18.0-372.9.1.rt7.166.el8, kernel-rt-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-kvm 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-core 4.18.0-372.9.1.rt7.166.el8, +4 more
    fixed: vendor fix RHSA-2022:1975
  • Red Hat Enterprise Linux NFV EUS (v.8.4) kernel-rt 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-kvm 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-core 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-modules 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-debug-kvm 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-debug-core 4.18.0-305.65.1.rt7.137.el8_4, +4 more
    fixed: vendor fix RHSA-2022:6991
  • Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-372.9.1.rt7.166.el8, kernel-rt-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-core 4.18.0-372.9.1.rt7.166.el8, kernel-rt-debug-modules 4.18.0-372.9.1.rt7.166.el8, kernel-rt-modules-extra 4.18.0-372.9.1.rt7.166.el8, +2 more
    fixed: vendor fix RHSA-2022:1975
show 2 more
  • Red Hat Enterprise Linux RT EUS (v.8.4) kernel-rt 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-core 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-modules 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-debug-core 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-debug-modules 4.18.0-305.65.1.rt7.137.el8_4, kernel-rt-modules-extra 4.18.0-305.65.1.rt7.137.el8_4, +2 more
    fixed: vendor fix RHSA-2022:6991
  • Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +83 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

0.40% chance of exploitation in the next 30 days, higher than 34% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 3.5 CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
NVD 2.0 2.7 AV:A/AC:L/Au:S/C:P/I:N/A:N

Classification

Weakness
  • CWE-327 Use of a Broken or Risky Cryptographic Algorithm
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.