A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free…

published 2021-05-26 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-18330

cvss: 7.0; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.0%; EPSS 1.0% chance of exploitation in 30 days, percentile 63%
public exploits: 0; none known

A flaw was found in Linux Kernel because access to the global variable fg_console is not properly synchronized leading to a use after free in con_font_op.

Patch / fix

fixed in 1 distros 4 links 3

linux linux_kernel 4.4.242, 4.9.242, 4.14.204, 4.19.155, 5.4.75, 5.9.5

debian ubuntu suse opensuse

linux Debian 14, Debian 13, Debian 12 5.9.6-1

debian advisories DEBIAN-CVE-2020-25668

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-2020-25668

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-syms SLES for SAP 12 SP2, SLES 12 SP2-LTSS, SLES 12 SP2-BCL +1 more 4.4.121-92.149.1
kernel-source SLES for SAP 12 SP2, SLES 12 SP2-LTSS, SLES 12 SP2-BCL +1 more 4.4.121-92.149.1
kernel-default SLES for SAP 12 SP2, SLES 12 SP2-LTSS, SLES 12 SP2-BCL +2 more 4.4.121-92.149.1
kgraft-patch-SLE12-SP2_Update_39 SLES for SAP 12 SP2, SLES 12 SP2-LTSS, OpenStack Cloud 7 1-3.3.1
kernel-syms SLE Module for Development Tools 15 SP2 5.3.18-24.43.2
kernel-source SLE Module for Development Tools 15 SP2, SLE Module for Basesystem 15 SP2 5.3.18-24.43.2
kernel-default SLE Workstation Extension 15 SP2, SLE Module for Legacy 15 SP2, SLE Module for Basesystem 15 SP2 +2 more 5.3.18-24.43.2
kernel-preempt SLE Module for Development Tools 15 SP2, SLE Module for Basesystem 15 SP2 5.3.18-24.43.2

suse advisories SUSE-SU-2021:14630-1 SUSE-SU-2021:0437-1 SUSE-SU-2020:3748-1 SUSE-SU-2020:3717-1 SUSE-SU-2020:3715-1 SUSE-SU-2020:3713-1

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-lp152.57.1.lp152.8.17.1
kernel-default-base openSUSE Leap 15.2 5.3.18-lp152.50.1.lp152.8.10.1

opensuse advisories openSUSE-SU-2024:10728-1 openSUSE-SU-2024:13704-1 openSUSE-SU-2021:0242-1 openSUSE-SU-2020:2260-1 openSUSE-SU-2020:2112-1 openSUSE-SU-2020:1906-1

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-2020-25668 updated 2026-11-06 cvss 0.0

kernel: race condition in fg_console can lead to use-after-free in con_font_op

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 Linux 8 perf, kernel, bpftool, kernel-rt, kernel-core, kernel-tools, +29 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

1.03% chance of exploitation in the next 30 days, higher than 63% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

openwall.com http://www.openwall.com/lists/oss-security/2020/10/30/1 referenced PoC, tagged "exploit" by a source, unverified
openwall.com http://www.openwall.com/lists/oss-security/2020/11/04/3 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	7.0	CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	6.9	AV:L/AC:M/Au:N/C:C/I:C/A:C

Affected products

n/a Linux Kernel

Classification

Weakness

CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
CWE-662 Improper Synchronization

Technology feeds

Linux kernel rss critical rss

References

git.kernel.org /pub/scm/linux/kernel/git/torvalds/linux.git/commit?id=90bfdeef83f1d6c696039b6a917190dcbbad3220
mailing-list, patch, third-party-advisory
openwall.com /lists/oss-security/2020/10/30/1
mailing-list, exploit, patch, third-party-advisory
openwall.com /lists/oss-security/2020/11/04/3
mailing-list, exploit, patch, third-party-advisory
lists.debian.org /debian-lts-announce/2020/12/msg00015.html
mailing-list, third-party-advisory
lists.debian.org /debian-lts-announce/2020/12/msg00027.html
mailing-list, third-party-advisory
openwall.com /lists/oss-security/2020/11/04/3%2C
openwall.com /lists/oss-security/2020/10/30/1%2C
bugzilla.redhat.com /show_bug.cgi?id=1893287%2C
security.netapp.com /advisory/ntap-20210702-0005/
third-party-advisory

Sources

CVE List CVE-2020-25668
NVD CVE-2020-25668

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.

Summary