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Fencer Vulns
high 7.8

CVE-2020-12657 json

An issue was discovered in the Linux kernel before 5.6.5.

published 2020-05-05 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-4956

cvss
7.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.7%
EPSS 0.7% chance of exploitation in 30 days, percentile 53%
public exploits
0
none known

Summary

An issue was discovered in the Linux kernel before 5.6.5. There is a use-after-free in block/bfq-iosched.c related to bfq_idle_slice_timer_body.

Patch / fix

  • linux linux_kernel 5.6.5
  • linux Debian 14, Debian 13, Debian 12 5.6.7-1

debian advisories DEBIAN-CVE-2020-12657

  • linux Ubuntu 18.04 LTS 4.15.0-101.102
  • linux Ubuntu 20.04 LTS 5.4.0-31.35
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1067.71
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1011.11
  • linux-gcp Ubuntu 16.04 LTS 4.15.0-1071.81~16.04.1
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1011.11
  • linux-hwe Ubuntu 16.04 LTS 4.15.0-101.102~16.04.1
  • linux-hwe Ubuntu 18.04 LTS 5.3.0-53.47~18.04.1

ubuntu advisories UBUNTU-CVE-2020-12657

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

  • kpatch-patch-4_18_0-193 RHEL 8 1-3.el8
  • kpatch-patch-4_18_0-193_1_2 RHEL 8 1-1.el8_2
  • kernel RHEL 8 4.18.0-193.6.3.el8_2
  • perf RHEL 8 4.18.0-193.6.3.el8_2
  • bpftool RHEL 8 4.18.0-193.6.3.el8_2
  • kernel-core RHEL 8 4.18.0-193.6.3.el8_2
  • kernel-tools RHEL 8 4.18.0-193.6.3.el8_2
  • python3-perf RHEL 8 4.18.0-193.6.3.el8_2

red hat advisories RHSA-2020:2429RHSA-2020:2567RHSA-2020:2669RHSA-2020:2667RHSA-2020:2427RHSA-2020:2428

  • kernel-rt Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-syms-rt Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-rt_debug Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-source-rt Real Time Module 15 SP1 4.12.14-14.28.1
  • kernel-rt SLE Real Time 12 SP5 4.12.14-10.13.1
  • kernel-syms-rt SLE Real Time 12 SP5 4.12.14-10.13.1
  • kernel-rt_debug SLE Real Time 12 SP5 4.12.14-10.13.1
  • kernel-source-rt SLE Real Time 12 SP5 4.12.14-10.13.1

suse advisories SUSE-SU-2020:2487-1SUSE-SU-2020:2478-1SUSE-SU-2020:2156-1SUSE-SU-2020:1663-1SUSE-SU-2020:1605-1SUSE-SU-2020:1604-1

  • kernel-syms openSUSE Leap 15.1 4.12.14-lp151.28.52.1
  • kernel-obs-qa openSUSE Leap 15.1 4.12.14-lp151.28.52.3
  • kernel-source openSUSE Leap 15.1 4.12.14-lp151.28.52.1
  • kernel-default openSUSE Leap 15.1 4.12.14-lp151.28.52.1
  • kernel-vanilla openSUSE Leap 15.1 4.12.14-lp151.28.52.1
  • kernel-kvmsmall openSUSE Leap 15.1 4.12.14-lp151.28.52.1
  • kernel-obs-build openSUSE Leap 15.1 4.12.14-lp151.28.52.3

opensuse advisories openSUSE-SU-2020:0801-1

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-2020-12657 updated cvss 7.0

kernel: use-after-free in block/bfq-iosched.c related to bfq_idle_slice_timer_body

  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-193.6.3.el8_2, kernel-debuginfo-common-aarch64 4.18.0-193.6.3.el8_2, kernel-debuginfo-common-ppc64le 4.18.0-193.6.3.el8_2
    fixed: vendor fix RHSA-2020:2427
  • Red Hat CodeReady Linux Builder EUS (v. 8.1) kernel-debuginfo-common-x86_64 4.18.0-147.20.1.el8_1, kernel-debuginfo-common-aarch64 4.18.0-147.20.1.el8_1, kernel-debuginfo-common-ppc64le 4.18.0-147.20.1.el8_1
    fixed: vendor fix RHSA-2020:2667
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-193.6.3.el8_2, kernel 4.18.0-193.6.3.el8_2, bpftool 4.18.0-193.6.3.el8_2, kpatch-patch-4_18_0-193 1-3.el8, kernel-core 4.18.0-193.6.3.el8_2, kernel-tools 4.18.0-193.6.3.el8_2, +17 more
    fixed: vendor fix RHSA-2020:2427
  • Red Hat Enterprise Linux BaseOS E4S (v. 8.0) perf 4.18.0-80.23.2.el8_0, kernel 4.18.0-80.23.2.el8_0, bpftool 4.18.0-80.23.2.el8_0, kernel-core 4.18.0-80.23.2.el8_0, kernel-tools 4.18.0-80.23.2.el8_0, python3-perf 4.18.0-80.23.2.el8_0, +9 more
    fixed: vendor fix RHSA-2020:2429
  • Red Hat Enterprise Linux BaseOS EUS (v. 8.1) perf 4.18.0-147.20.1.el8_1, kernel 4.18.0-147.20.1.el8_1, bpftool 4.18.0-147.20.1.el8_1, kpatch-patch-4_18_0-147 1-14.el8, kernel-core 4.18.0-147.20.1.el8_1, kernel-tools 4.18.0-147.20.1.el8_1, +22 more
    fixed: vendor fix RHSA-2020:2667
  • Red Hat Enterprise Linux Real Time (v. 8) kernel-rt 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-core 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-modules 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-debug-core 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-debug-modules 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-modules-extra 4.18.0-193.6.3.rt13.59.el8_2, +2 more Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-kvm 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-core 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-modules 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-debug-kvm 4.18.0-193.6.3.rt13.59.el8_2, kernel-rt-debug-core 4.18.0-193.6.3.rt13.59.el8_2, +4 more
    fixed: vendor fix RHSA-2020:2428
  • Red Hat Enterprise Linux 5 kernel 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 MRG 2 kernel-rt, mrg-rt-release, kernel-rt-trace, kernel-rt-vanilla, kernel-rt-firmware
    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

0.71% chance of exploitation in the next 30 days, higher than 53% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 7.8 CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 4.6 AV:L/AC:L/Au:N/C:P/I:P/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.