CVE-2021-20219

Publication date 23 March 2021

Last updated 25 August 2025

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.5 · Medium

Score breakdown

Description

A denial of service vulnerability was found in n_tty_receive_char_special in drivers/tty/n_tty.c of the Linux kernel. In this flaw a local attacker with a normal user privilege could delay the loop (due to a changing ldata->read_head, and a missing sanity check) and cause a threat to the system availability.

Read the notes from the security team

Status

Package Ubuntu Release Status
linux-azure 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic Ignored superseded by linux-azure-5.3
16.04 LTS xenial
Not affected
14.04 LTS trusty Ignored was not-affected (Red Hat specific) ESM criteria
linux-azure-4.15 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-azure-5.3 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-azure-5.4
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-azure-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-azure-edge 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-azure-5.3
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-dell300x 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gcp 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic Ignored superseded by linux-gcp-5.3
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-gcp-4.15 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gcp-5.3 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-gcp-5.4
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gcp-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gcp-edge 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-gcp-5.3
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-4.15 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored end of life, was not-affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-5.0 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored end of standard support, was not-affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-5.3 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gke-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gkeop 20.10 groovy Not in release
20.04 LTS focal
Not affected
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-gkeop-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-hwe-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-hwe-5.8 20.10 groovy Not in release
20.04 LTS focal
Not affected
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-hwe-edge 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-hwe-5.4
16.04 LTS xenial Ignored superseded by linux-hwe
14.04 LTS trusty Not in release
linux-kvm 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-lts-trusty 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-lts-xenial 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Ignored was not-affected (Red Hat specific) ESM criteria
linux-oem 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored end of life, was not-affected
16.04 LTS xenial Ignored end of standard support
14.04 LTS trusty Not in release
linux-oem-5.10 20.10 groovy Not in release
20.04 LTS focal
Not affected
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oem-5.6 20.10 groovy Not in release
20.04 LTS focal
Not affected
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oracle 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-oracle-5.0 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-oracle-5.3
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oracle-5.3 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-oracle-5.4
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-oracle-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-raspi2-5.3 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-riscv 20.10 groovy
Not affected
20.04 LTS focal Ignored end of life, was not-affected
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-snapdragon 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
linux-aws-5.0 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-aws-5.3
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-hwe 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored replaced by linux-hwe-5.4
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-aws 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Ignored was not-affected (Red Hat specific) ESM criteria
linux-aws-5.3 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored superseded by linux-aws-5.4
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-aws-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-aws-hwe 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Not in release
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
linux-oem-osp1 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic Ignored end of standard support, was not-affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-raspi 20.10 groovy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic Not in release
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-raspi-5.4 20.10 groovy Not in release
20.04 LTS focal Not in release
18.04 LTS bionic
Not affected
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
linux-raspi2 20.10 groovy Not in release
20.04 LTS focal Ignored replaced by linux-raspi
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release

Notes

sbeattie

Red Hat's backport of 3d63b7e4ae0d "n_tty: Fix stall at n_tty_receive_char_special()." was incomplete and could result in an infinite loop.

Severity score breakdown

Parameter Value
Base score 5.5 · Medium
Attack vector Local
Attack complexity Low
Privileges required Low
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact None
Availability impact High
Vector CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

References

Other references