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Fencer Vulns
medium 5.0

CVE-2020-28974 json

A slab-out-of-bounds read in fbcon in the Linux kernel before 5.9.7 could be used by local attackers to read privileged information or pote…

published 2020-11-20 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-21358

cvss
5.0
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

A slab-out-of-bounds read in fbcon in the Linux kernel before 5.9.7 could be used by local attackers to read privileged information or potentially crash the kernel, aka CID-3c4e0dff2095. This occurs because KD_FONT_OP_COPY in drivers/tty/vt/vt.c can be used for manipulations such as font height.

Patch / fix

  • linux linux_kernel 5.9.7
  • linux Debian 14, Debian 13, Debian 12 5.9.9-1

debian advisories DEBIAN-CVE-2020-28974

  • 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-2020-28974

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 4.18.0-305.el8
  • perf RHEL 8 4.18.0-305.el8
  • bpftool RHEL 8 4.18.0-305.el8
  • kernel-core RHEL 8 4.18.0-305.el8
  • kernel-tools RHEL 8 4.18.0-305.el8
  • python3-perf RHEL 8 4.18.0-305.el8
  • kernel-modules RHEL 8 4.18.0-305.el8
  • kernel-zfcpdump RHEL 8 4.18.0-305.el8

red hat advisories RHSA-2021:1578RHSA-2021:1739

  • kernel-syms SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 4.4.180-94.138.1
  • kernel-source SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +4 more 4.4.180-94.138.1
  • kernel-default SLES for SAP 12 SP3, SLES 12 SP3-LTSS, SLES 12 SP3-BCL +5 more 4.4.180-94.138.1
  • kgraft-patch-SLE12-SP3_Update_37 SLES for SAP 12 SP3, SLES 12 SP3-LTSS, OpenStack Cloud Crowbar 8 +3 more 1-4.3.1
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.66.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.66.1
  • kernel-default SLES for SAP 15, SLES 15-LTSS, SLE Live Patching 15 +3 more 4.12.14-150.66.1
  • kernel-vanilla SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.66.1

suse advisories SUSE-SU-2021:14630-1SUSE-SU-2021:0452-1SUSE-SU-2021:0438-1SUSE-SU-2021:0437-1SUSE-SU-2021:0434-1SUSE-SU-2020:3798-1

  • 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-lp152.57.1.lp152.8.17.1
  • kernel-syms openSUSE Leap 15.1 4.12.14-lp151.28.87.1
  • kernel-obs-qa openSUSE Leap 15.1 4.12.14-lp151.28.87.2
  • kernel-source openSUSE Leap 15.1 4.12.14-lp151.28.87.1

opensuse advisories openSUSE-SU-2021:0242-1openSUSE-SU-2020:2260-1openSUSE-SU-2020:2193-1openSUSE-SU-2020:2161-1

  • linux Arch Linux 5.9.7.arch1-1

arch linux advisories AVG-1313

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-2020-28974 updated cvss 5.0

kernel: slab-out-of-bounds read in fbcon

  • Red Hat Enterprise Linux 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more
    affected: workaround, no fix planned “Out of support scope”
  • 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
    affected: workaround, no fix planned “Will not fix”
  • Red Hat CodeReady Linux Builder (v. 8) kernel-debuginfo-common-x86_64 4.18.0-305.el8, kernel-debuginfo-common-aarch64 4.18.0-305.el8, kernel-debuginfo-common-ppc64le 4.18.0-305.el8 Red Hat Enterprise Linux BaseOS (v. 8) perf 4.18.0-305.el8, kernel 4.18.0-305.el8, bpftool 4.18.0-305.el8, kernel-core 4.18.0-305.el8, kernel-tools 4.18.0-305.el8, python3-perf 4.18.0-305.el8, +15 more
    fixed: vendor fix RHSA-2021:1578
  • Red Hat Enterprise Linux Real Time (v. 8) kernel-rt 4.18.0-305.rt7.72.el8, kernel-rt-core 4.18.0-305.rt7.72.el8, kernel-rt-modules 4.18.0-305.rt7.72.el8, kernel-rt-debug-core 4.18.0-305.rt7.72.el8, kernel-rt-debug-modules 4.18.0-305.rt7.72.el8, kernel-rt-modules-extra 4.18.0-305.rt7.72.el8, +2 more Red Hat Enterprise Linux Real Time for NFV (v. 8) kernel-rt 4.18.0-305.rt7.72.el8, kernel-rt-kvm 4.18.0-305.rt7.72.el8, kernel-rt-core 4.18.0-305.rt7.72.el8, kernel-rt-modules 4.18.0-305.rt7.72.el8, kernel-rt-debug-kvm 4.18.0-305.rt7.72.el8, kernel-rt-debug-core 4.18.0-305.rt7.72.el8, +4 more
    fixed: vendor fix RHSA-2021:1739

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

0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • seclists.org https://seclists.org/oss-sec/2020/q4/104 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 5.0 CVSS:3.1/AV:P/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:H
NVD 2.0 6.1 AV:L/AC:L/Au:N/C:P/I:P/A:C

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.