A x11vnc security update has been released for Debian GNU/Linux 10 to address a flaw in x11vnc.

DSA 4799-1: x11vnc security update

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Debian Security Advisory DSA-4799-1 security@debian.org
  https://www.debian.org/security/ Salvatore Bonaccorso
November 28, 2020   https://www.debian.org/security/faq
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Package : x11vnc
CVE ID : CVE-2020-29074
Debian Bug : 975875

Guenal Davalan reported a flaw in x11vnc, a VNC server to allow remote
access to an existing X session. x11vnc creates shared memory segments
with 0777 mode. A local attacker can take advantage of this flaw for
information disclosure, denial of service or interfering with the VNC
session of another user on the host.

For the stable distribution (buster), this problem has been fixed in
version 0.9.13-6+deb10u1.

We recommend that you upgrade your x11vnc packages.

For the detailed security status of x11vnc please refer to its security
tracker page at:
  https://security-tracker.debian.org/tracker/x11vnc

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