CVE-2021-28711

Publication date 5 January 2022

Last updated 10 September 2026

Ubuntu priority

Low

Why this priority?

Cvss 3 Severity Score

6.5 · Medium

Score breakdown

Description

Rogue backends can cause DoS of guests via high frequency events T[his CNA information record relates to multiple CVEs; the text explains which aspects/vulnerabilities correspond to which CVE.] Xen offers the ability to run PV backends in regular unprivileged guests, typically referred to as "driver domains". Running PV backends in driver domains has one primary security advantage: if a driver domain gets compromised, it doesn't have the privileges to take over the system. However, a malicious driver domain could try to attack other guests via sending events at a high frequency leading to a Denial of Service in the guest due to trying to service interrupts for elongated amounts of time. There are three affected backends: * blkfront patch 1, CVE-2021-28711 * netfront patch 2, CVE-2021-28712 * hvc_xen (console) patch 3, CVE-2021-28713

From the Ubuntu Security Team

Jürgen Groß discovered that the Xen subsystem within the Linux kernel did not adequately limit the number of events driver domains (unprivileged PV backends) could send to other guest VMs. An attacker in a driver domain could use this to cause a denial of service in other guest VMs.

Read the notes from the security team

Status

Package Ubuntu Release Status
linux-gke 26.04 LTS resolute
Not affected
25.10 questing Not in release
25.04 plucky Not in release
24.10 oracular Not in release
24.04 LTS noble
Not affected
23.10 mantic Not in release
23.04 lunar Not in release
22.10 kinetic Not in release
22.04 LTS jammy
Not affected
21.10 impish Not in release
21.04 hirsute Not in release
20.04 LTS focal
Fixed 5.4.0-1066.69
18.04 LTS bionic Not in release
16.04 LTS xenial Ignored end of standard support
14.04 LTS trusty Not in release
linux-azure-fde-5.15 26.04 LTS resolute Not in release
25.10 questing Not in release
25.04 plucky Not in release
24.10 oracular Not in release
24.04 LTS noble Not in release
23.10 mantic Not in release
23.04 lunar Not in release
22.10 kinetic Not in release
22.04 LTS jammy 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-xilinx 26.04 LTS resolute Not in release
25.10 questing Not in release
25.04 plucky
Not affected
24.04 LTS noble
Not affected
22.04 LTS jammy 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-nvidia-bos 26.04 LTS resolute
Not affected
25.10 questing Not in release
24.04 LTS noble Not in release
22.04 LTS jammy 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-nvidia-7.0 26.04 LTS resolute Not in release
25.10 questing Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-hwe-7.0 26.04 LTS resolute Not in release
25.10 questing Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-oem-7.0 26.04 LTS resolute
Not affected
25.10 questing Not in release
24.04 LTS noble Not in release
22.04 LTS jammy 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-aws-7.0 26.04 LTS resolute Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-riscv-7.0 26.04 LTS resolute Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-azure-7.0 26.04 LTS resolute Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-azure-fde-7.0 26.04 LTS resolute Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-gcp-7.0 26.04 LTS resolute Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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-oracle-7.0 26.04 LTS resolute Not in release
24.04 LTS noble
Not affected
22.04 LTS jammy 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 26.04 LTS resolute
Not affected
25.10 questing
Not affected
25.04 plucky
Not affected
24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
21.10 impish
Fixed 5.13.0-37.42
21.04 hirsute Ignored end of life
20.04 LTS focal
Fixed 5.4.0-105.119
18.04 LTS bionic
Fixed 4.15.0-169.177
16.04 LTS xenial
Fixed 4.4.0-239.273
14.04 LTS trusty Ignored end of standard support, was needed
linux-allwinner 26.04 LTS resolute Not in release
25.10 questing Not in release
25.04 plucky Not in release
24.10 oracular Not in release
24.04 LTS noble Not in release
23.10 mantic Not in release
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy 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-allwinner-5.19 26.04 LTS resolute Not in release
25.10 questing Not in release
25.04 plucky Not in release
24.10 oracular Not in release
24.04 LTS noble Not in release
23.10 mantic Not in release
23.04 lunar Not in release
22.10 kinetic Not in release
22.04 LTS jammy
Not affected
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-aws 26.04 LTS resolute
Not affected
25.10 questing
Not affected
25.04 plucky
Not affected
24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Not affected
23.04 lunar
Not affected
22.10 kinetic
Not affected
22.04 LTS jammy
Not affected
21.10 impish
Fixed 5.13.0-1019.21
21.04 hirsute Ignored end of life
20.04 LTS focal
Fixed 5.4.0-1069.73
18.04 LTS bionic
Fixed 4.15.0-1121.129
16.04 LTS xenial Ignored end of standard support, was needed
14.04 LTS trusty Ignored end of standard support, was needed
linux-aws-5.0 26.04 LTS