A tigervnc security update has been released for Debian GNU/Linux 9 LTS to address an issue where viewer implementation mishandles TLS certificate exceptions.

DLA 2396-1: tigervnc security update

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Debian LTS Advisory DLA-2396-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Roberto C. Sánchez
October 06, 2020   https://wiki.debian.org/LTS
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Package : tigervnc
Version : 1.7.0+dfsg-7+deb9u2
CVE ID : CVE-2020-26117
Debian Bug : 971272

A vulnerability was discovered in tigernvc, a Virtual Network Computing
client and server implementation. The viewer implementation mishandles
TLS certificate exceptions, storing the certificates as authorities,
meaning that the owner of a certificate could impersonate any server
after a client had added an exception.

For Debian 9 stretch, this problem has been fixed in version
1.7.0+dfsg-7+deb9u2.

We recommend that you upgrade your tigervnc packages.

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

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