A Linux kernel security update has been released for Ubuntu Linux 21.04.

==========================================================================
Ubuntu Security Notice USN-4997-1
June 23, 2021

linux, linux-aws, linux-azure, linux-gcp, linux-oracle, linux-raspi
vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 21.04

Summary:

Several security issues were fixed in the Linux 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-oracle: Linux kernel for Oracle Cloud systems
- linux-raspi: Linux kernel for Raspberry Pi (V8) systems

Details:

Norbert Slusarek discovered a race condition in the CAN BCM networking
protocol of the Linux kernel leading to multiple use-after-free
vulnerabilities. A local attacker could use this issue to execute arbitrary
code. (CVE-2021-3609)

Piotr Krysiuk discovered that the eBPF implementation in the Linux kernel
did not properly enforce limits for pointer operations. A local attacker
could use this to cause a denial of service (system crash) or possibly
execute arbitrary code. (CVE-2021-33200)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation did
not properly clear received fragments from memory in some situations. A
physically proximate attacker could possibly use this issue to inject
packets or expose sensitive information. (CVE-2020-24586)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation
incorrectly handled encrypted fragments. A physically proximate attacker
could possibly use this issue to decrypt fragments. (CVE-2020-24587)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation
incorrectly handled certain malformed frames. If a user were tricked into
connecting to a malicious server, a physically proximate attacker could use
this issue to inject packets. (CVE-2020-24588)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation
incorrectly handled EAPOL frames from unauthenticated senders. A physically
proximate attacker could inject malicious packets to cause a denial of
service (system crash). (CVE-2020-26139)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation did
not properly verify certain fragmented frames. A physically proximate
attacker could possibly use this issue to inject or decrypt packets.
(CVE-2020-26141)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation
accepted plaintext fragments in certain situations. A physically proximate
attacker could use this issue to inject packets. (CVE-2020-26145)

Mathy Vanhoef discovered that the Linux kernel’s WiFi implementation could
reassemble mixed encrypted and plaintext fragments. A physically proximate
attacker could possibly use this issue to inject packets or exfiltrate
selected fragments. (CVE-2020-26147)

Or Cohen discovered that the SCTP implementation in the Linux kernel
contained a race condition in some situations, leading to a use-after-free
condition. A local attacker could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2021-23133)

Or Cohen and Nadav Markus discovered a use-after-free vulnerability in the
nfc implementation in the Linux kernel. A privileged local attacker could
use this issue to cause a denial of service (system crash) or possibly
execute arbitrary code. (CVE-2021-23134)

Manfred Paul discovered that the extended Berkeley Packet Filter (eBPF)
implementation in the Linux kernel contained an out-of-bounds
vulnerability. A local attacker could use this issue to execute arbitrary
code. (CVE-2021-31440)

Piotr Krysiuk discovered that the eBPF implementation in the Linux kernel
did not properly prevent speculative loads in certain situations. A local
attacker could use this to expose sensitive information (kernel memory).
(CVE-2021-31829)

It was discovered that a race condition in the kernel Bluetooth subsystem
could lead to use-after-free of slab objects. An attacker could use this
issue to possibly execute arbitrary code. (CVE-2021-32399)

It was discovered that a use-after-free existed in the Bluetooth HCI driver
of the Linux kernel. A local attacker could use this to cause a denial of
service (system crash) or possibly execute arbitrary code. (CVE-2021-33034)

It was discovered that an out-of-bounds (OOB) memory access flaw existed in
the f2fs module of the Linux kernel. A local attacker could use this issue
to cause a denial of service (system crash). (CVE-2021-3506)

Mathias Krause discovered that a null pointer dereference existed in the
Nitro Enclaves kernel driver of the Linux kernel. A local attacker could
use this issue to cause a denial of service or possibly execute arbitrary
code. (CVE-2021-3543)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 21.04:
  linux-image-5.11.0-1009-azure   5.11.0-1009.9
  linux-image-5.11.0-1010-oracle  5.11.0-1010.10
  linux-image-5.11.0-1011-aws     5.11.0-1011.11
  linux-image-5.11.0-1011-gcp     5.11.0-1011.12
  linux-image-5.11.0-1012-raspi   5.11.0-1012.13
  linux-image-5.11.0-1012-raspi-nolpae  5.11.0-1012.13
  linux-image-5.11.0-22-generic   5.11.0-22.23
  linux-image-5.11.0-22-generic-64k  5.11.0-22.23
  linux-image-5.11.0-22-generic-lpae  5.11.0-22.23
  linux-image-5.11.0-22-lowlatency  5.11.0-22.23
  linux-image-aws                 5.11.0.1011.11
  linux-image-azure               5.11.0.1009.9
  linux-image-gcp                 5.11.0.1011.11
  linux-image-generic             5.11.0.22.23
  linux-image-generic-64k         5.11.0.22.23
  linux-image-generic-lpae        5.11.0.22.23
  linux-image-gke                 5.11.0.1011.11
  linux-image-lowlatency          5.11.0.22.23
  linux-image-oracle              5.11.0.1010.10
  linux-image-raspi               5.11.0.1012.10
  linux-image-raspi-nolpae        5.11.0.1012.10
  linux-image-virtual             5.11.0.22.23

After a standard system update you need to reboot your computer to make
all the necessary changes.

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

References:
    https://ubuntu.com/security/notices/USN-4997-1
  CVE-2020-24586, CVE-2020-24587, CVE-2020-24588, CVE-2020-26139,
  CVE-2020-26141, CVE-2020-26145, CVE-2020-26147, CVE-2021-23133,
  CVE-2021-23134, CVE-2021-31440, CVE-2021-31829, CVE-2021-32399,
  CVE-2021-33034, CVE-2021-33200, CVE-2021-3506, CVE-2021-3543,
  CVE-2021-3609

Package Information:
    https://launchpad.net/ubuntu/+source/linux/5.11.0-22.23
    https://launchpad.net/ubuntu/+source/linux-aws/5.11.0-1011.11
    https://launchpad.net/ubuntu/+source/linux-azure/5.11.0-1009.9
    https://launchpad.net/ubuntu/+source/linux-gcp/5.11.0-1011.12
    https://launchpad.net/ubuntu/+source/linux-oracle/5.11.0-1010.10
    https://launchpad.net/ubuntu/+source/linux-raspi/5.11.0-1012.13