A qemu regression update has been released for Debian GNU/Linux 9 LTS to address a regression which prevented ssh connections to the host system.

DLA 2753-2: qemu regression update

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Debian LTS Advisory DLA-2753-2 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Markus Koschany
September 11, 2021   https://wiki.debian.org/LTS
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Package : qemu
Version : 1:2.8+dfsg-6+deb9u16
CVE ID : CVE-2021-3592
Debian Bug : 994080

It was found that the patch for CVE-2021-3592 introduced a regression which
prevented ssh connections to the host system. Since there is no imminent
solution for the problem, the patch for CVE-2021-3592 has been reverted.
Updated qemu packages are now available to correct this issue.

For Debian 9 stretch, this problem has been fixed in version
1:2.8+dfsg-6+deb9u16.

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