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______________________________________________________________________________

			SCO Security Advisory

Subject:		OpenServer 5.0.6 OpenServer 5.0.7 : A vulnerability in TCP 
Advisory number: 	SCOSA-2005.3
Issue date: 		2005 February 28
Cross reference:	sr890248 fz529385 erg712599 CAN-2004-0230
______________________________________________________________________________


1. Problem Description

	TCP, when using a large Window Size, makes it easier for
	remote attackers to guess sequence numbers and cause a
	denial of service (connection loss) to persistent TCP
	connections by repeatedly injecting a TCP RST packet,
	especially in protocols that use long-lived connections,
	such as BGP. 

	Paul Watson performed a statistical analysis of this attack 
	when the ISN is not known and has pointed out that such an 
	attack could be viable when specifically taking into account 
	the TCP Window size. He has also created a proof-of-concept 
	tool demonstrating the practicality of the attack. 

	The National Infrastructure Security Co-Ordination Center (NISCC) 
	has published an advisory summarizing Paul Watson's analysis in 
	"NISCC Vulnerability Advisory 236929." 

	The Common Vulnerabilities and Exposures project (cve.mitre.org)
	has assigned the name CAN-2004-0230 to this issue.


2. Vulnerable Supported Versions

	System				Binaries
	----------------------------------------------------------------------
	OpenServer 5.0.6 		TCP driver
	OpenServer 5.0.7 		TCP driver

3. Solution

	The proper solution is to install the latest packages.


4. OpenServer 5.0.7

	4.1 Location of Fixed Binaries

	ftp://ftp.sco.com/pub/updates/OpenServer/SCOSA-2005.3

	4.2 Verification

	MD5 (VOL.000.000) = 0f3182ee23d7bd90359d7ac0973dd44e

	md5 is available for download from
		ftp://ftp.sco.com/pub/security/tools

	4.3 Installing Fixed Binaries

	Upgrade the affected binaries with the following sequence:

	1) Download the VOL* files to the /tmp directory

	2) Run the custom command, specify an install from media
	images, and specify the /tmp directory as the location of
	the images.

5. OpenServer 5.0.6

	5.1 Location of Fixed Binaries

	ftp://ftp.sco.com/pub/updates/OpenServer/SCOSA-2005.3

	5.2 Verification

	MD5 (VOL.000.000) = 0f3182ee23d7bd90359d7ac0973dd44e

	md5 is available for download from
		ftp://ftp.sco.com/pub/security/tools

	5.3 Installing Fixed Binaries

	Upgrade the affected binaries with the following sequence:

	1) Download the VOL* files to the /tmp directory

	2) Run the custom command, specify an install from media
	images, and specify the /tmp directory as the location of
	the images.

6. References

	Specific references for this advisory:
		http://www.uniras.gov.uk/vuls/2004/236929/index.htm 
		http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2004-0230 
		http://www.us-cert.gov/cas/techalerts/TA04-111A.html

	SCO security resources:
		http://www.sco.com/support/security/index.html

	SCO security advisories via email
		http://www.sco.com/support/forums/security.html

	This security fix closes SCO incidents sr890248 fz529385
	erg712599.


7. Disclaimer

	SCO is not responsible for the misuse of any of the information
	we provide on this website and/or through our security
	advisories. Our advisories are a service to our customers
	intended to promote secure installation and use of SCO
	products.


8. Acknowledgments

	SCO would like to thank The National Infrastructure Security
	Co-Ordination Centre (NISCC), Paul Watson and Tim Newsham.

______________________________________________________________________________


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