Published:
07 February 2002
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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2002.064 -- Microsoft Security Bulletin MS02-004 Unchecked Buffer in Telnet Server Could Lead to Arbitrary Code Execution 8 February 2002 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Telnet Service in Microsoft Windows 2000 Telnet Daemon in Microsoft Interix 2.2 Vendor: Microsoft Impact: Denial of Service Execute Arbitrary Code/Commands Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- - - - - - ---------------------------------------------------------------------- Title: Unchecked Buffer in Telnet Server Could Lead to Arbitrary Code Execution Date: 07 February 2002 Software: Telnet Service in Microsoft Windows 2000; Telnet Daemon in Microsoft Interix 2.2 Impact: Denial of Service; Possibly Run Code of Attacker's Choice Max Risk: Moderate Bulletin: MS02-004 Microsoft encourages customers to review the Security Bulletin at: http://www.microsoft.com/technet/security/bulletin/MS02-004.asp. - - - - - ---------------------------------------------------------------------- Issue: ====== The Telnet protocol provides remote shell capabilities. Microsoft has implemented the Telnet protocol by providing a Telnet Server in several products. The implementations in two of these products - - - - Windows 2000 and Interix 2.2 - contain unchecked buffers in the code that handles the processing of telnet protocol options. An attacker could use this vulnerability to perform a buffer overflow attack. A successful attack could cause the Telnet Server to fail, or in some cases, could possibly allow an attacker to execute code of her choice on the system. Such code would execute using the security context of the Telnet service, but this context varies from product to product. In Windows 2000, the Telnet service always runs as System; in the Interix implementation, the administrator selects the security context in which to run as part of the installation process. Mitigating Factors: ==================== - While the Telnet Service in Windows 2000 is installed by default, it is not running by default. As a result, a Windows 2000 system would only be vulnerable if the administrator had started the service - Remotely exploiting this vulnerability would require the attacker to have the ability to connect to the Telnet Server. Best practices recommends against allowing Telnet access on uncontrolled networks. - The Telnet Daemon in Interix 2.2 is not installed by default when Interix 2.2 is installed. An administrator would have to choose to install and configure this feature. - The Telnet Daemon in Interix does not specify a security context by default. The administrator specifies the security context when they configure or run the daemon. Best practices recommend that the Telnet Daemon run in a context of least privilege, meaning that it have only those rights necessary and no more. Risk Rating: ============ - Internet systems: Moderate - Intranet systems: Moderate - Client systems: Moderate Patch Availability: =================== - A patch is available to fix this vulnerability. Please read the Security Bulletin at http://www.microsoft.com/technet/security/bulletin/ms02-004.asp for information on obtaining this patch. - - - - - --------------------------------------------------------------------- THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND. MICROSOFT DISCLAIMS ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL, CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES. 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Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: auscert@auscert.org.au Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for emergencies. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBPGP7nih9+71yA2DNAQG4nAP+IncCsqAkEtyZbbcr49dPMf7ltXj1BW8Y 3CfXTTfJy9/NxArgIppf4gbZu5MnrJY1IeNR3PRrZrQ67L8IreO5gfNtuhrSxxb0 CySskfuJFzLVlF9CnsFkMl0AHH+GXiYZ3iE38XX017uUYcv7XIRrYWl+bxBgJrxI RCyxahrWISY= =/NS7 -----END PGP SIGNATURE-----