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x11vnc: Authentication bypass in included LibVNCServer code


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200608-12 / x11vnc
Release Date August 07, 2006
Latest Revision August 07, 2006: 01
Impact high
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
x11-misc/x11vnc < 0.8.1 >= 0.8.1 All supported architectures

Related bugreports: #142559


VNC servers created with x11vnc accept insecure protocol types, even when the server does not offer it, resulting in the possibility of unauthorized access to the server.

2.  Impact Information


x11vnc provides VNC servers for X displays.


x11vnc includes vulnerable LibVNCServer code, which fails to properly validate protocol types effectively letting users decide what protocol to use, such as "Type 1 - None" (GLSA-200608-05). x11vnc will accept this security type, even if it is not offered by the server.


An attacker could exploit this vulnerability to gain unauthorized access with the privileges of the user running the VNC server.

3.  Resolution Information


There is no known workaround at this time.


All x11vnc users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=x11-misc/x11vnc-0.8.1"

4.  References


Page updated August 07, 2006

Summary: This is a Gentoo Linux Security Advisory

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