A linux security update has been released for Debian GNU/Linux 9 LTS.

DLA 2843-1: linux security update

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Debian LTS Advisory DLA-2843-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Ben Hutchings
December 16, 2021   https://wiki.debian.org/LTS
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Package : linux
Version : 4.9.290-1
CVE ID : CVE-2020-3702 CVE-2020-16119 CVE-2021-0920 CVE-2021-3612
CVE-2021-3653 CVE-2021-3655 CVE-2021-3679 CVE-2021-3732
CVE-2021-3753 CVE-2021-3760 CVE-2021-20317 CVE-2021-20321
CVE-2021-20322 CVE-2021-22543 CVE-2021-37159 CVE-2021-38160
CVE-2021-38198 CVE-2021-38199 CVE-2021-38204 CVE-2021-38205
CVE-2021-40490 CVE-2021-41864 CVE-2021-42008 CVE-2021-42739
CVE-2021-43389

Several vulnerabilities have been discovered in the Linux kernel that
may lead to a privilege escalation, denial of service, or information
leaks.

CVE-2020-3702

A flaw was found in the driver for Atheros IEEE 802.11n family of
chipsets (ath9k) allowing information disclosure.

CVE-2020-16119

Hadar Manor reported a use-after-free in the DCCP protocol
implementation in the Linux kernel. A local attacker can take
advantage of this flaw to cause a denial of service or potentially
to execute arbitrary code.

CVE-2021-0920

A race condition was discovered in the local sockets (AF_UNIX)
subsystem, which could lead to a use-after-free. A local user
could exploit this for denial of service (memory corruption or
crash), or possibly for privilege escalation.

CVE-2021-3612

Murray McAllister reported a flaw in the joystick input subsystem.
A local user permitted to access a joystick device could exploit
this to read and write out-of-bounds in the kernel, which could
be used for privilege escalation.

CVE-2021-3653

Maxim Levitsky discovered a vulnerability in the KVM hypervisor
implementation for AMD processors in the Linux kernel: Missing
validation of the `int_ctl` VMCB field could allow a malicious L1
guest to enable AVIC support (Advanced Virtual Interrupt
Controller) for the L2 guest. The L2 guest can take advantage of
this flaw to write to a limited but still relatively large subset
of the host physical memory.

CVE-2021-3655

Ilja Van Sprundel and Marcelo Ricardo Leitner found multiple flaws
in the SCTP implementation, where missing validation could lead to
an out-of-bounds read. On a system using SCTP, a networked
attacker could exploit these to cause a denial of service (crash).

CVE-2021-3679

A flaw in the Linux kernel tracing module functionality could
allow a privileged local user (with CAP_SYS_ADMIN capability) to
cause a denial of service (resource starvation).

CVE-2021-3732

Alois Wohlschlager reported a flaw in the implementation of the
overlayfs subsystem, allowing a local attacker with privileges to
mount a filesystem to reveal files hidden in the original mount.

CVE-2021-3753

Minh Yuan reported a race condition in the vt_k_ioctl in
drivers/tty/vt/vt_ioctl.c, which may cause an out of bounds read
in vt.

CVE-2021-3760

Lin Horse reported a flaw in the NCI (NFC Controller Interface)
driver, which could lead to a use-after-free.

However, this driver is not included in the binary packages
provided by Debian.

CVE-2021-20317

It was discovered that the timer queue structure could become
corrupt, leading to waiting tasks never being woken up. A local
user with certain privileges could exploit this to cause a denial
of service (system hang).

CVE-2021-20321

A race condition was discovered in the overlayfs filesystem
driver. A local user with access to an overlayfs mount and to its
underlying upper directory could exploit this for privilege
escalation.

CVE-2021-20322

An information leak was discovered in the IPv4 implementation. A
remote attacker could exploit this to quickly discover which UDP
ports a system is using, making it easier for them to carry out a
DNS poisoning attack against that system.

CVE-2021-22543

David Stevens discovered a flaw in how the KVM hypervisor maps
host memory into a guest. A local user permitted to access
/dev/kvm could use this to cause certain pages to be freed when
they should not, leading to a use-after-free. This could be used
to cause a denial of service (crash or memory corruption) or
possibly for privilege escalation.

CVE-2021-37159

A flaw was discovered in the hso driver for Option mobile
broadband modems. An error during initialisation could lead to a
double-free or use-after-free. An attacker able to plug in USB
devices could use this to cause a denial of service (crash or
memory corruption) or possibly to run arbitrary code.

CVE-2021-38160

A flaw in the virtio_console was discovered allowing data
corruption or data loss by an untrusted device.

CVE-2021-38198

A flaw was discovered in the KVM implementation for x86
processors, that could result in virtual memory protection within
a guest not being applied correctly. When shadow page tables are
used - i.e. for nested virtualisation, or on CPUs lacking the EPT
or NPT feature - a user of the guest OS might be able to exploit
this for denial of service or privilege escalation within the
guest.

CVE-2021-38199

Michael Wakabayashi reported a flaw in the NFSv4 client
implementation, where incorrect connection setup ordering allows
operations of a remote NFSv4 server to cause a denial of service.

CVE-2021-38204

A flaw was discovered in the max4321-hcd USB host controller
driver, which could lead to a use-after-free.

However, this driver is not included in the binary packages
provided by Debian.

CVE-2021-38205

An information leak was discovered in the xilinx_emaclite network
driver. On a custom kernel where this driver is enabled and used,
this might make it easier to exploit other kernel bugs.

CVE-2021-40490

A race condition was discovered in the ext4 subsystem when writing
to an inline_data file while its xattrs are changing. This could
result in denial of service.

CVE-2021-41864

An integer overflow was discovered in the Extended BPF (eBPF)
subsystem. A local user could exploit this for denial of service
(memory corruption or crash), or possibly for privilege
escalation.

This can be mitigated by setting sysctl
kernel.unprivileged_bpf_disabled=1, which disables eBPF use by
unprivileged users.

CVE-2021-42008

A heap buffer overflow was discovered in the 6pack serial port
network driver. A local user with CAP_NET_ADMIN capability could
exploit this for denial of service (memory corruption or crash), or
possibly for privilege escalation.

CVE-2021-42739

A heap buffer overflow was discovered in the firedtv driver for
FireWire-connected DVB receivers. A local user with access to a
firedtv device could exploit this for denial of service (memory
corruption or crash), or possibly for privilege escalation.

CVE-2021-43389

The Active Defense Lab of Venustech discovered a flaw in the CMTP
subsystem as used by Bluetooth, which could lead to an
out-of-bounds read and object type confusion. A local user with
CAP_NET_ADMIN capability in the initial user namespace could
exploit this for denial of service (memory corruption or crash),
or possibly for privilege escalation.

For Debian 9 stretch, these problems have been fixed in version
4.9.290-1.

We recommend that you upgrade your linux packages.

For the detailed security status of linux please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/linux

Further information about Debian LTS security advisories, how to apply
these updates to your system and frequently asked questions can be
found at:   https://wiki.debian.org/LTS

Ben Hutchings
Humans are not rational beings; they are rationalising beings.