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LibVNCServer: Authentication bypass


1.  Gentoo Linux Security Advisory

Version Information

Advisory Reference GLSA 200608-05 / libvncserver
Release Date August 04, 2006
Latest Revision August 04, 2006: 01
Impact high
Exploitable remote
Package Vulnerable versions Unaffected versions Architecture(s)
net-libs/libvncserver < 0.8.2 >= 0.8.2 All supported architectures

Related bugreports: #136916


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

2.  Impact Information


LibVNCServer is a GPL'ed library for creating VNC servers.


LibVNCServer fails to properly validate protocol types effectively letting users decide what protocol to use, such as "Type 1 - None". LibVNCServer will accept this security type, even if it is not offered by the server.


An attacker could use 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 LibVNCServer users should upgrade to the latest version:

Code Listing 3.1: Resolution

# emerge --sync
# emerge --ask --oneshot --verbose ">=net-libs/libvncserver-0.8.2"

4.  References


Page updated August 04, 2006

Summary: This is a Gentoo Linux Security Advisory

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