DNS Cache Poisoning appears to be a big and fast-growing problem. Windows and Bind users should review number 1 below for a description of the problem and how to block it. Separately, if you are using Windows 2003, definitely explore Service Pack 1 for a slew of important security improvements.
Alan
@RISK is the SANS community's consensus bulletin summarizing the most important vulnerabilities and exploits identified during the past week and providing guidance on appropriate actions to protect your systems (PART I). It also includes a comprehensive list of all new vulnerabilities discovered in the past week (PART II).
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Part I is compiled by Rohit Dhamankar (rohitd_at_tippingpoint.com) at TippingPoint, a division of 3Com, as a by-product of that company's continuous effort to ensure that its intrusion prevention products effectively block exploits using known vulnerabilities. TippingPoint's analysis is complemented by input from a council of security managers from twelve large organizations who confidentially share with SANS the specific actions they have taken to protect their systems. A detailed description of the process may be found at http://www.sans.org/newsletters/cva/#process
Description: SANS Internet Storm Center (ISC) has been actively analyzing reports of large-scale DNS cache poisoning attacks underway. By performing the DNS cache poisoning, an attacker is able to direct traffic intended for legitimate domains (for instance, windowsupdate.com) to an IP address under the attacker's control. The attacks have been used to re-direct popular domains belonging to a number of financial, entertainment, travel, health and software companies to the attackers' servers in order to install malware on the user systems. The attacks are targeting flaws in the Symantec Gateway security products (described in an earlier @RISK newsletter), and the forwarding configurations using Windows and BIND DNS servers listed above.
Status: Microsoft has published an article KB241352 that describes how to set up a registry key on Windows 2000 (prior to SP3) and NT 4.0 (SP4 and later) to harden a DNS server's configuration. An upgrade to version 9.x for the DNS forwarding servers running BIND is recommended. An upgrade to Windows 2000 (SP3 or above) and Windows 2003 is recommended for Windows DNS servers since these versions offer protection against the cache poisoning attacks in their default configuration. Symantec has already released updates for its DNS products that should be immediately applied. ISC has also detailed steps on how to clean the current DNS cache, which may be polluted.
Council Site Actions: Most of the reporting council sites are running only UNIX-based DNS and BIND servers with safe configurations and thus are not vulnerable to this issue. A few sites running Windows versions have either confirmed their configurations are safe or have updated them, as necessary. One site is implementing a rapid response plan based on a previous risk assessment of this threat situation.
Description: The Jet Database Engine (Msjet40.dll) is Microsoft's relational database engine that handles the entire task of database processing for Microsoft Access and Visual Basic. This engine reportedly contains a buffer overflow that can be triggered by a specially crafted ".mdb" Access database file. The flaw, according to the discoverer, can be easily exploited to execute code on a Windows client system. In order to exploit this flaw, an attacker has to supply the malicious .mdb file via web, email, peer-to-peer sharing etc to the victim. Note that Internet Explorer and other browsers do not automatically open the attacker-supplied ".mdb" file. Hence, user interaction is required to leverage this flaw. A proof-of-concept database file has been publicly posted. The discoverer also mentions other denial-of-service flaws in this DLL for which no technical details have been posted.
Status: Microsoft has not confirmed; no patches are available. The flaw also affects third party applications that use msjet40.dll.
Council Site Actions: Most of the council sites are waiting for confirmation and a patch from the vendor and plan to deploy the patch once available. One site commented they have no plans to patch at this time, and will instead rely on their implementation of the Cisco Security Agent to prevent this exploit from occurring.
Description: PHP, the popular scripting language for web servers, contains two vulnerabilities in its "getimagesize()" function. This function is used to compute the size of many image formats such as GIFF, JPEG etc. An attacker can exploit these flaws to cause a denial of service to any webserver that is using PHP scripts( and the getimagesize() function) to process the user-supplied images. The technical details required to craft a malicious image file have been publicly posted.
Status: Upgrade to PHP version 4.3.11 or 5.0.4.
Council Site Actions: Only one of the reporting council sites is using the affects software and feature. Their servers will be updated through a vendor patch (e.g., a patch associated with a Linux distribution) rather than updated with software obtained directly from www.php.net.
Description: Bakbone Netvault is a backup solution for environments running UNIX, Linux, Windows NT/2000/2003 or Netware. The software is reportedly being used by AT&T, Los Alamos National Laboratory and many other large enterprises. The implementation of the communication protocol between the Netvault client (the system being backed up) and the server (the system backing up the data) contains a heap-based buffer overflow. By sending specially crafted packets to the port 20031/tcp, an attacker can execute arbitrary code on the system running this software. Exploit code for leveraging this flaw on Windows platforms is publicly available.
Status: Vendor not confirmed, no updates available. A workaround is to block the ports 20031/tcp and 20031/udp (the Netvault default ports) at the network perimeter. Increased scanning activity has been noticed for the port 20031/tcp.
Council Site Actions: The affected software is not in production or widespread use, or is not officially supported at any of the council sites. They reported that no action was necessary.
Description: MailEnable, a Windows-based mail server, contains buffer overflows in its IMAP server (MEIMAPS.EXE). An unauthenticated attacker can trigger the flaw by sending an overlong argument to the "AUTHENTICATE" or "LOGIN" commands. The flaws can be exploited to execute arbitrary code with the privileges of the IMAP server. Exploit code has been publicly posted.
Status: Vendor has confirmed the buffer overflow in the "AUTHENTICATE" command and released hotfixes. The status of hotfixes for the "LOGIN" command overflow is unknown.
Council Site Actions: The affected software is not in production or widespread use, or is not officially supported at any of the council sites. They reported that no action was necessary.
Description: Microsoft has released Service Pack 1 for Windows 2003. This update includes many security features such as Windows firewall, enhanced memory checks to protect against buffer overflows, protection from malicious e-mail and more authentication checks for RPC services.
Description: After an initial push back from Sybase, NGSSoftware has finally released the technical details regarding the vulnerabilities in the Sybase Adaptive Server Enterprise that were patched in December 2004. The Sybase administrators should apply the patches as soon as possible, if they have not already done so.
This list is compiled by Qualys ( www.qualys.com ) as part of that company's ongoing effort to ensure its vulnerability management web service tests for all known vulnerabilities that can be scanned. As of this week Qualys scans for 4201 unique vulnerabilities. For this special SANS community listing, Qualys also includes vulnerabilities that cannot be scanned remotely.
(c) 2005. All rights reserved. The information contained in this newsletter, including any external links, is provided "AS IS," with no express or implied warranty, for informational purposes only. In some cases, copyright for material in this newsletter may be held by a party other than Qualys (as indicated herein) and permission to use such material must be requested from the copyright owner.
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