Details can be found in the Qualys advisory at
https://www.qualys.com/2022/01/25/cve-2021-4034/pwnkit.txt
For Debian 9 stretch, this problem has been fixed in version
0.105-18+deb9u2.
We recommend that you upgrade your policykit-1 packages.
For the detailed security status of policykit-1 please refer to its
security tracker page at:
https://security-tracker.debian.org/tracker/source-package/policykit-1
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
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