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[oCERT-2014-007] libvncserver multiple issues
#2014-007 libvncserver multiple issues
Virtual Network Computing (VNC) is a graphical sharing system based on the
Remote Frame Buffer (RFB) protocol.
The LibVNCServer project, an open source library for implementing VNC
compliant communication, suffers from a number of bugs that can be potentially
exploited with security impact.
Various implementation issues resulting in remote code execution and/or DoS
conditions on both the VNC server and client side have been discovered.
1. A malicious VNC server can trigger incorrect memory management
handling by advertising a large screen size parameter to the VNC
client. This would result in multiple memory corruptions and could
allow remote code execution on the VNC client.
2. A malicious VNC client can trigger multiple DoS conditions on the VNC
server by advertising a large screen size, ClientCutText message
length and/or a zero scaling factor parameter.
3. A malicious VNC client can trigger multiple stack-based buffer
overflows by passing a long file and directory names and/or attributes
(FileTime) when using the file transfer message feature.
It should be noted that every described issue represents a post-authentication
bug, therefore the server side conditions can be anonymously leveraged only if
the VNC server is configured to allow unauthenticated sessions.
LibVNCServer <= 0.9.9
Credit: vulnerability report received from Nicolas Ruff
of Google Security Team <nruff AT google.com>.
CVE: CVE-2014-6051 (1), CVE-2014-6052 (1), CVE-2014-6053 (2),
CVE-2014-6054 (2), CVE-2014-6055 (3)
2014-09-05: vulnerability report received
2014-09-16: contacted affected vendors
2014-09-22: contacted additional affected vendors
2014-09-25: advisory release
Andrea Barisani | Founder & Project Coordinator
oCERT | OSS Computer Security Incident Response Team
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"Pluralitas non est ponenda sine necessitate"