==========================================================================
Ubuntu Security Notice USN-6439-1
October 19, 2023

linux, linux-aws, linux-kvm, linux-lts-xenial vulnerabilities
==========================================================================

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

- Ubuntu 16.04 LTS (Available with Ubuntu Pro)
- Ubuntu 14.04 LTS (Available with Ubuntu Pro)

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-kvm: Linux kernel for cloud environments
- linux-lts-xenial: Linux hardware enablement kernel from Xenial for Trusty

Details:

It was discovered that the IPv6 implementation in the Linux kernel
contained a high rate of hash collisions in connection lookup table. A
remote attacker could use this to cause a denial of service (excessive CPU
consumption). (CVE-2023-1206)

Yu Hao and Weiteng Chen discovered that the Bluetooth HCI UART driver in
the Linux kernel contained a race condition, leading to a null pointer
dereference vulnerability. A local attacker could use this to cause a
denial of service (system crash). (CVE-2023-31083)

Ross Lagerwall discovered that the Xen netback backend driver in the Linux
kernel did not properly handle certain unusual packets from a
paravirtualized network frontend, leading to a buffer overflow. An attacker
in a guest VM could use this to cause a denial of service (host system
crash) or possibly execute arbitrary code. (CVE-2023-34319)

Lin Ma discovered that the Netlink Transformation (XFRM) subsystem in the
Linux kernel contained a null pointer dereference vulnerability in some
situations. A local privileged attacker could use this to cause a denial of
service (system crash). (CVE-2023-3772)

Kyle Zeng discovered that the networking stack implementation in the Linux
kernel did not properly validate skb object size in certain conditions. An
attacker could use this cause a denial of service (system crash) or
possibly execute arbitrary code. (CVE-2023-42752)

Kyle Zeng discovered that the netfiler subsystem in the Linux kernel did
not properly calculate array offsets, leading to a out-of-bounds write
vulnerability. A local user could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2023-42753)

Kyle Zeng discovered that the IPv4 Resource Reservation Protocol (RSVP)
classifier implementation in the Linux kernel contained an out-of-bounds
read vulnerability. A local attacker could use this to cause a denial of
service (system crash). Please note that kernel packet classifier support
for RSVP has been removed to resolve this vulnerability. (CVE-2023-42755)

Bing-Jhong Billy Jheng discovered that the Unix domain socket
implementation in the Linux kernel contained a race condition in certain
situations, leading to a use-after-free vulnerability. A local attacker
could use this to cause a denial of service (system crash) or possibly
execute arbitrary code. (CVE-2023-4622)

Budimir Markovic discovered that the qdisc implementation in the Linux
kernel did not properly validate inner classes, leading to a use-after-free
vulnerability. A local user could use this to cause a denial of service
(system crash) or possibly execute arbitrary code. (CVE-2023-4623)

Alex Birnberg discovered that the netfilter subsystem in the Linux kernel
did not properly validate register length, leading to an out-of- bounds
write vulnerability. A local attacker could possibly use this to cause a
denial of service (system crash). (CVE-2023-4881)

It was discovered that the Quick Fair Queueing scheduler implementation in
the Linux kernel did not properly handle network packets in certain
conditions, leading to a use after free vulnerability. A local attacker
could use this to cause a denial of service (system crash) or possibly
execute arbitrary code. (CVE-2023-4921)

Update instructions:

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

Ubuntu 16.04 LTS (Available with Ubuntu Pro):
   linux-image-4.4.0-1125-kvm      4.4.0-1125.135
   linux-image-4.4.0-1162-aws      4.4.0-1162.177
   linux-image-4.4.0-246-generic   4.4.0-246.280
   linux-image-4.4.0-246-lowlatency  4.4.0-246.280
   linux-image-aws                 4.4.0.1162.166
   linux-image-generic             4.4.0.246.252
   linux-image-generic-lts-xenial  4.4.0.246.252
   linux-image-kvm                 4.4.0.1125.122
   linux-image-lowlatency          4.4.0.246.252
   linux-image-lowlatency-lts-xenial  4.4.0.246.252
   linux-image-virtual             4.4.0.246.252
   linux-image-virtual-lts-xenial  4.4.0.246.252

Ubuntu 14.04 LTS (Available with Ubuntu Pro):
   linux-image-4.4.0-246-generic   4.4.0-246.280~14.04.1
   linux-image-4.4.0-246-lowlatency  4.4.0-246.280~14.04.1
   linux-image-generic-lts-xenial  4.4.0.246.214
   linux-image-lowlatency-lts-xenial  4.4.0.246.214
   linux-image-virtual-lts-xenial  4.4.0.246.214

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-6439-1
   CVE-2023-1206, CVE-2023-31083, CVE-2023-34319, CVE-2023-3772,
   CVE-2023-42752, CVE-2023-42753, CVE-2023-42755, CVE-2023-4622,
   CVE-2023-4623, CVE-2023-4881, CVE-2023-4921