A Linux kernel security update has been released for Ubuntu Linux 14.04 ESM, 16.04 LTS, 18.04 LTS, and 20.04 LTS.

LSN-0076-1: Linux kernel vulnerability

Linux kernel vulnerabilities

A security issue affects these releases of Ubuntu and its derivatives:
- Ubuntu 20.04 LTS
- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS
- Ubuntu 14.04 ESM

Summary

Several security issues were fixed in the kernel.

Software Description

- linux - Linux kernel
- linux-aws - Linux kernel for Amazon Web Services (AWS) systems - linux-azure - Linux kernel for Microsoft Azure Cloud systems - linux-gcp - Linux kernel for Google Cloud Platform (GCP) systems - linux-gke - Linux kernel for Google Container Engine (GKE) systems - linux-gkeop - Linux kernel for Google Container Engine (GKE) systems
- linux-oem - Linux kernel for OEM systems

Details

It was discovered that the overlayfs implementation in the Linux kernel did not properly validate the application of file system capabilities with respect to user namespaces. A local attacker could use this to gain
elevated privileges. (CVE-2021-3493)

Piotr Krysiuk discovered that the BPF JIT compiler for x86 in the Linux kernel did not properly validate computation of branch displacements in some situations. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.
(CVE-2021-29154)

Update instructions

The problem can be corrected by updating your kernel livepatch to the following versions:

Ubuntu 20.04 LTS
aws - 76.3
azure - 76.3
gcp - 76.3
generic - 76.3
gke - 76.3
gkeop - 76.3
lowlatency - 76.3

Ubuntu 18.04 LTS
aws - 76.2
generic - 76.3
gke - 76.3
gkeop - 76.3
lowlatency - 76.3
oem - 76.2

Ubuntu 16.04 LTS
aws - 76.1
azure - 76.2
generic - 76.2
lowlatency - 76.2

Ubuntu 14.04 ESM
generic - 76.1
lowlatency - 76.1

Support Information

Kernels older than the levels listed below do not receive livepatch updates. If you are running a kernel version earlier than the one listed
below, please upgrade your kernel as soon as possible.

Ubuntu 20.04 LTS
linux-aws - 5.4.0-1009
linux-azure - 5.4.0-1010
linux-gcp - 5.4.0-1009
linux-gke - 5.4.0-1033
linux-gkeop - 5.4.0-1009
linux-oem - 5.4.0-26
linux - 5.4.0-26

Ubuntu 18.04 LTS
linux-aws - 4.15.0-1054
linux-gke-4.15 - 4.15.0-1076
linux-gke-5.4 - 5.4.0-1009
linux-gkeop-5.4 - 5.4.0-1007
linux-hwe-5.4 - 5.4.0-26
linux-oem - 4.15.0-1063
linux - 4.15.0-69

Ubuntu 16.04 LTS
linux-aws - 4.4.0-1098
linux-azure - 4.15.0-1063
linux-azure - 4.15.0-1078
linux-hwe - 4.15.0-69
linux - 4.4.0-168

Ubuntu 14.04 ESM
linux-lts-xenial - 4.4.0-168

References

- CVE-2021-3493
- CVE-2021-29154