A qemu security update has been released for Debian GNU/Linux to address several security vulnerabilities.

DLA 2753-1: qemu security update

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Debian LTS Advisory DLA-2753-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Markus Koschany
September 02, 2021   https://wiki.debian.org/LTS
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Package : qemu
Version : 1:2.8+dfsg-6+deb9u15
CVE ID : CVE-2021-3527 CVE-2021-3592 CVE-2021-3594 CVE-2021-3595
CVE-2021-3682 CVE-2021-3713
Debian Bug : 988157 989993 989995 989996 991911 992727

Several security vulnerabilities have been found in Qemu, a fast processor
emulator.

CVE-2021-3713

An out-of-bounds write flaw was found in the UAS (USB Attached SCSI) device
emulation of QEMU. The device uses the guest supplied stream number
unchecked, which can lead to out-of-bounds access to the UASDevice->data3
and UASDevice->status3 fields. A malicious guest user could use this flaw
to crash QEMU or potentially achieve code execution with the privileges of
the QEMU process on the host.

CVE-2021-3682

A flaw was found in the USB redirector device emulation of QEMU. It occurs
when dropping packets during a bulk transfer from a SPICE client due to the
packet queue being full. A malicious SPICE client could use this flaw to
make QEMU call free() with faked heap chunk metadata, resulting in a crash
of QEMU or potential code execution with the privileges of the QEMU process
on the host.

CVE-2021-3527

A flaw was found in the USB redirector device (usb-redir) of QEMU. Small
USB packets are combined into a single, large transfer request, to reduce
the overhead and improve performance. The combined size of the bulk
transfer is used to dynamically allocate a variable length array (VLA) on
the stack without proper validation. Since the total size is not bounded, a
malicious guest could use this flaw to influence the array length and cause
the QEMU process to perform an excessive allocation on the stack, resulting
in a denial of service.

CVE-2021-3594

An invalid pointer initialization issue was found in the SLiRP networking
implementation of QEMU. The flaw exists in the udp_input() function and
could occur while processing a udp packet that is smaller than the size of
the 'udphdr' structure. This issue may lead to out-of-bounds read access or
indirect host memory disclosure to the guest. The highest threat from this
vulnerability is to data confidentiality.

CVE-2021-3592

An invalid pointer initialization issue was found in the SLiRP networking
implementation of QEMU. The flaw exists in the bootp_input() function and
could occur while processing a udp packet that is smaller than the size of
the 'bootp_t' structure. A malicious guest could use this flaw to leak 10
bytes of uninitialized heap memory from the host. The highest threat from
this vulnerability is to data confidentiality.

CVE-2021-3595

An invalid pointer initialization issue was found in the SLiRP networking
implementation of QEMU. The flaw exists in the tftp_input() function and
could occur while processing a udp packet that is smaller than the size of
the 'tftp_t' structure. This issue may lead to out-of-bounds read access or
indirect host memory disclosure to the guest. The highest threat from this
vulnerability is to data confidentiality.

For Debian 9 stretch, these problems have been fixed in version
1:2.8+dfsg-6+deb9u15.

We recommend that you upgrade your qemu packages.

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

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