iDefense Security Advisory 12.09.05: Ethereal OSPF Protocol Dissector Buffer Overflow Vulnerability
Ethereal OSPF Protocol Dissector Buffer Overflow Vulnerability
iDefense Security Advisory 12.09.05
www.idefense.com/application/poi/display?id=349&type=vulnerabilities
December 9, 2005
I. BACKGROUND
Ethereal is a full featured open source network protocol analyzer.
For more information, see http://www.ethereal.com/
II. DESCRIPTION
Remote exploitation of an input validation vulnerability in the OSPF
protocol dissectors within Ethereal, as included in various vendors
operating system distributions, could allow attackers to crash the
vulnerable process or potentially execute arbitrary code.
The affected Ethereal component is used to analyse Open Shortest Path
First (OSPF) Interior Gateway Protocol (IGP), as specified in RFC-2178.
The vulnerability specifically exists due to no bounds checking being
performed in the dissect_ospf_v3_address_prefix() function. This
function takes user-supplied binary data and attempts to convert it into
a human readable string. This function uses a fixed length buffer on
the stack to store the constructed string but performs no checks on the
length of the input. If the generated output length from the input
exceeds the size of the buffer, a stack-based overflow occurs.
III. ANALYSIS
Successful exploitation allows remote attackers to perform a DoS against
a running instance of Ethereal and may, under certain conditions,
potentially allow the execution of arbitrary code. As the overflow
string is generated from a format string converting binary values into
their hexadecimal (base 16) equivalent characters, it can contain only a
limited subset of all possible characters, and the length of an
overflow is only able to be controlled to within the three characters.
This may prevent exploit ability on some platforms; however, it may be
possible that these constraints will not prevent exploitation on
others.
IV. DETECTION
iDefense has confirmed the existence of this vulnerability in the
ethereal-0.10.12 RPM from Red Hat Fedora Core 3. It is suspected that
previous versions containing the OSPF dissector code are also
vulnerable.
V. WORKAROUND
Disable the OSPF packet dissector in Ethereal by performing the
following actions as the user invoking Ethereal, typically root.
Create the .ethereal directory:
# mkdir ~/.ethereal
You can safely ignore the following error:
mkdir: cannot create directory '/root/.ethereal': File exists
Add the OSPF dissector to the list of protocols to ignore.
# echo ospf >> ~/.ethereal/disabled_protos
This workaround will prevent Ethereal from parsing the contents of OSPF
packets, which prevents exposure to the vulnerability.
VI. VENDOR RESPONSE
A source patch is available from the main ethereal SVN Repository:
http://anonsvn.ethereal.com/viewcvs/viewcvs.py/trunk/epan/dissectors/
packet-ospf.c?rev=16507&view=markup
VII. CVE INFORMATION
The Common Vulnerabilities and Exposures (CVE) project has assigned the
name CVE-2005-3651 to this issue. This is a candidate for inclusion in
the CVE list (http://cve.mitre.org), which standardizes names for
security problems.
VIII. DISCLOSURE TIMELINE
11/14/2005 Initial vendor notification
11/14/2005 Initial vendor response
12/09/2005 Public disclosure
IX. CREDIT
The discoverer of this vulnerability wishes to remain anonymous.
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X. LEGAL NOTICES
Copyright © 2005 iDefense, Inc.
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Disclaimer: The information in the advisory is believed to be accurate
at the time of publishing based on currently available information. Use
of the information constitutes acceptance for use in an AS IS condition.
There are no warranties with regard to this information. Neither the
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or consequential loss or damage arising from use of, or reliance on,
this information.