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Fencer Intel
medium 4.1

CVE-2020-25656 json

A flaw was found in the Linux kernel.

published 5y ago modified 4mo ago also EUVD-2020-18320

cvss
4.1
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 38%
public exploits
0
none known

Summary

A flaw was found in the Linux kernel. A use-after-free was found in the way the console subsystem was using ioctls KDGKBSENT and KDSKBSENT. A local user could use this flaw to get read memory access out of bounds. The highest threat from this vulnerability is to data confidentiality.

Patch / fix

  • linux linux_kernel 5.10
  • linux Debian 14, Debian 13, Debian 12 5.9.6-1

debian advisories DEBIAN-CVE-2020-25656

  • linux Ubuntu 16.04 LTS 4.4.0-198.230
  • linux Ubuntu 18.04 LTS 4.15.0-129.132
  • linux Ubuntu 20.04 LTS 5.4.0-59.65
  • linux-aws Ubuntu 16.04 LTS 4.4.0-1119.133
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1091.96
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1034.35
  • linux-gcp Ubuntu 16.04 LTS 4.15.0-1091.104~16.04.1
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1033.35

ubuntu advisories UBUNTU-CVE-2020-25656

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 RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-kvm RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-core RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-modules RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-debug-kvm RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-debug-core RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-debug-modules RHEL 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-modules-extra RHEL 8 4.18.0-553.rt7.342.el8_10

red hat advisories RHSA-2024:2950RHSA-2024:3138RHSA-2021:0856RHSA-2021:0857

  • kernel-syms SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.65.1
  • kernel-source SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.65.1
  • kernel-default SLES for SAP 12 SP4, SLES 12 SP4-LTSS, SLE Live Patching 12 SP4 +3 more 4.12.14-95.65.1
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.63.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.63.1
  • kernel-default SLES for SAP 15, SLES 15-LTSS, SLE Live Patching 15 +3 more 4.12.14-150.63.1
  • kernel-vanilla SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.63.1
  • kernel-obs-build SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.63.1

suse advisories SUSE-SU-2021:14630-1SUSE-SU-2020:3544-1SUSE-SU-2020:3532-1SUSE-SU-2020:3522-1SUSE-SU-2020:3513-1SUSE-SU-2020:3512-1

  • kernel-source openSUSE Tumbleweed 5.14.6-1.4
  • kernel-source openSUSE Tumbleweed 6.6.17-1.1
  • kernel-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-syms-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-rt_debug openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-source-rt openSUSE Leap 15.2 5.3.18-lp152.3.5.1
  • kernel-default-base openSUSE Leap 15.2 5.3.18-lp152.50.1.lp152.8.10.1
  • kernel-syms openSUSE Leap 15.2 5.3.18-lp152.50.1

opensuse advisories openSUSE-SU-2024:10728-1openSUSE-SU-2024:13704-1openSUSE-SU-2021:0242-1openSUSE-SU-2020:2112-1openSUSE-SU-2020:1906-1

  • kernel-rt AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-kvm AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-core AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-modules AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-debug-kvm AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-debug-core AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-debug-modules AlmaLinux 8 4.18.0-553.rt7.342.el8_10
  • kernel-rt-modules-extra AlmaLinux 8 4.18.0-553.rt7.342.el8_10

almalinux advisories ALSA-2024:2950ALSA-2024:3138

  • kernel Rocky Linux 8 4.18.0-553.123.1.el8_10.cloud.0.1
  • kernel-rt Rocky Linux 8 4.18.0-553.rt7.342.el8_10
  • kernel Rocky Linux 8 4.18.0-553.el8_10

rocky linux advisories RXSA-2024:3138RLSA-2024:2950RLSA-2024:3138

Is CVE-2020-25656 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.

Check with Fencer

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-2020-25656 updated cvss 4.1

kernel: use-after-free in read in vt_do_kdgkb_ioctl

  • Red Hat Enterprise Linux 7 perf, kernel, kernel-alt, python-perf, kernel-kdump, kernel-tools, +3 more
    affected: no fix planned “Will not fix”
  • Red Hat Enterprise MRG 2 kernel
    affected: no fix planned “Out of support scope”
  • Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-553.el8_10, kernel 4.18.0-553.el8_10, bpftool 4.18.0-553.el8_10, kernel-core 4.18.0-553.el8_10, kernel-tools 4.18.0-553.el8_10, python3-perf 4.18.0-553.el8_10, +15 more
    fixed: vendor fix RHSA-2024:3138
  • 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 CRB (v. 8) kernel-debuginfo-common-x86_64 4.18.0-553.el8_10, kernel-debuginfo-common-aarch64 4.18.0-553.el8_10, kernel-debuginfo-common-ppc64le 4.18.0-553.el8_10
    fixed: vendor fix RHSA-2024:3138
  • 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 NFV (v. 8) kernel-rt 4.18.0-553.rt7.342.el8_10, kernel-rt-kvm 4.18.0-553.rt7.342.el8_10, kernel-rt-core 4.18.0-553.rt7.342.el8_10, kernel-rt-modules 4.18.0-553.rt7.342.el8_10, kernel-rt-debug-kvm 4.18.0-553.rt7.342.el8_10, kernel-rt-debug-core 4.18.0-553.rt7.342.el8_10, +4 more Red Hat Enterprise Linux RT (v. 8) kernel-rt 4.18.0-553.rt7.342.el8_10, kernel-rt-core 4.18.0-553.rt7.342.el8_10, kernel-rt-modules 4.18.0-553.rt7.342.el8_10, kernel-rt-debug-core 4.18.0-553.rt7.342.el8_10, kernel-rt-debug-modules 4.18.0-553.rt7.342.el8_10, kernel-rt-modules-extra 4.18.0-553.rt7.342.el8_10, +2 more
    fixed: vendor fix RHSA-2024:2950
  • 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 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
show 1 more
  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 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

0.44% chance of exploitation in the next 30 days, higher than 38% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • bugzilla.redhat.com https://bugzilla.redhat.com/show_bug.cgi?id=1888726 referenced PoC, tagged "exploit" by a source, unverified
  • lkml.org https://lkml.org/lkml/2020/10/16/84 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 4.1 CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 1.9 AV:L/AC:M/Au:N/C:P/I:N/A:N

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.