Skip to content
Fencer Intel
medium 4.7

CVE-2021-3753 json

A race problem was seen in the vt_k_ioctl in drivers/tty/vt/vt_ioctl.c in the Linux kernel, which may cause an out of bounds read in vt as…

published 4y ago modified 4mo ago also EUVD-2021-27028

cvss
4.7
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 30%
public exploits
0
none known

Summary

A race problem was seen in the vt_k_ioctl in drivers/tty/vt/vt_ioctl.c in the Linux kernel, which may cause an out of bounds read in vt as the write access to vc_mode is not protected by lock-in vt_ioctl (KDSETMDE). The highest threat from this vulnerability is to data confidentiality.

Patch / fix

  • linux linux_kernel 5.15
  • linux Debian 14, Debian 13, Debian 12 5.14.6-1

debian advisories DEBIAN-CVE-2021-3753

  • linux Ubuntu 18.04 LTS 4.15.0-162.170
  • linux Ubuntu 20.04 LTS 5.4.0-90.101
  • linux-aws Ubuntu 18.04 LTS 4.15.0-1115.122
  • linux-aws Ubuntu 20.04 LTS 5.4.0-1059.62
  • linux-gcp Ubuntu 20.04 LTS 5.4.0-1057.61
  • linux-gke Ubuntu 20.04 LTS 5.4.0-1055.58
  • linux-ibm Ubuntu 20.04 LTS 5.4.0-1007.8
  • linux-kvm Ubuntu 18.04 LTS 4.15.0-1102.104

ubuntu advisories UBUNTU-CVE-2021-3753

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-2024:3138

  • kernel-syms SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.83.2
  • kernel-source SLES for SAP 12 SP4, SLES 12 SP4-LTSS, OpenStack Cloud Crowbar 9 +1 more 4.12.14-95.83.2
  • kernel-default SLES for SAP 12 SP4, SLES 12 SP4-LTSS, SLE Live Patching 12 SP4 +3 more 4.12.14-95.83.2
  • kernel-syms SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-source SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-default SLES for SAP 15, SLES 15-LTSS, SLE Live Patching 15 +3 more 4.12.14-150.78.1
  • kernel-vanilla SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.1
  • kernel-obs-build SLES for SAP 15, SLES 15-LTSS, SLE High Performance Computing 15-LTSS +1 more 4.12.14-150.78.2

suse advisories SUSE-SU-2022:14905-1SUSE-SU-2021:3972-1SUSE-SU-2021:3969-1SUSE-SU-2021:3935-1SUSE-SU-2021:3929-1SUSE-SU-2021:3876-1

  • kernel-source openSUSE Tumbleweed 5.14.6-1.4
  • kernel-source openSUSE Tumbleweed 6.6.17-1.1
  • kernel-default openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-vanilla openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-kvmsmall openSUSE Leap 15.3 4.12.14-197.102.2
  • kernel-zfcpdump openSUSE Leap 15.3 4.12.14-197.102.2
  • dtb-aarch64 openSUSE Leap 15.3 5.3.18-59.24.1
  • kernel-64kb openSUSE Leap 15.3 5.3.18-59.24.1

opensuse advisories openSUSE-SU-2024:10728-1openSUSE-SU-2024:13704-1openSUSE-SU-2021:3876-1openSUSE-SU-2021:3205-1openSUSE-SU-2021:3179-1openSUSE-SU-2021:1271-1

  • 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

  • linux Arch Linux 5.14.2.arch1-2
  • linux-zen Arch Linux 5.14.2.zen1-2
  • linux-hardened Arch Linux 5.13.14.hardened1-1
  • linux-lts Arch Linux 5.10.62-1

arch linux advisories AVG-2346AVG-2347AVG-2348AVG-2349

Is CVE-2021-3753 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-2021-3753 updated cvss 4.7

kernel: a race out-of-bound read in vt

  • Red Hat Enterprise Linux 7 perf, kernel, bpftool, kernel-rt, python-perf, kernel-kdump, +8 more
    affected: workaround, 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 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 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 5 kernel Red Hat Enterprise Linux 6 perf, kernel, python-perf, kernel-kdump, kernel-firmware, kernel-bootwrapper, +1 more Red Hat Enterprise Linux 9 rv, perf, rtla, kernel, bpftool, libperf, +81 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

0.36% chance of exploitation in the next 30 days, higher than 30% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • openwall.com https://www.openwall.com/lists/oss-security/2021/09/01/4 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 4.7 CVSS:3.1/AV:L/AC:H/PR:L/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
  • CWE-125 Out-of-bounds Read
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization
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.