[SA19513] UltrVNC Buffer Overflow Vulnerabilities

From: Secunia Security Advisories (sec-advsecunia.com)
Date: Wed Apr 05 2006 - 04:47:05 CDT

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TITLE:
UltrVNC Buffer Overflow Vulnerabilities

SECUNIA ADVISORY ID:
SA19513

VERIFY ADVISORY:
http://secunia.com/advisories/19513/

CRITICAL:
Moderately critical

IMPACT:
DoS, System access

WHERE:
From remote

SOFTWARE:
UltrVNC 1.x
http://secunia.com/product/2836/

DESCRIPTION:
Luigi Auriemma has reported two vulnerabilities in UltrVNC, which
can be exploited by malicious people to cause a DoS (Denial of
Service) and potentially compromise a vulnerable system.

1) A boundary error exists in the "Log::ReallyPrint()" client
function when logging replies received from a VNC server during
login. This can be exploited to cause a buffer overflow on a client
system via a "connection failed" error response with an overly long
string.

Successful exploitation may allow execution of arbitrary code on a
client system when e.g. connecting to a malicious VNC server.

2) A boundary error in the "VNCLog::ReallyPrint()" function when
logging information can be exploited to cause a buffer overflow. This
may crash the VNC service or allow execution of arbitrary code.

Successful exploitation requires that an administrative user has
changed the default "Log debug infos to the WinVNC.log file" setting
in the configuration. Systems are still vulnerable even when this
setting has been changed back to the default state.

The vulnerabilities have been reported in version 1.0.1. Other
versions may also be affected.

SOLUTION:
A patch will reportedly be released in the next weeks.

PROVIDED AND/OR DISCOVERED BY:
Luigi Auriemma

ORIGINAL ADVISORY:
http://aluigi.altervista.org/adv/uvncbof-adv.txt

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