===================================================================== CERT-Renater Note d'Information No. 2006/VULN414 _____________________________________________________________________ DATE : 28/07/2006 HARDWARE PLATFORM(S) : / OPERATING SYSTEM(S) : Solaris 8, Solaris 9, Solaris 10. ====================================================================== Sun(sm) Alert Notification * Sun Alert ID: 102206 * Synopsis: Solaris Hosts are Vulnerable to a Denial of Service Induced by an Internet Transmission Control Protocol (TCP) "ACK Storm" * Category: Security * Product: Solaris 9 Operating System, Solaris 10 Operating System, Solaris 8 Operating System * BugIDs: 4511681 * Avoidance: Patch * State: Resolved * Date Released: 26-Jul-2006 * Date Closed: 26-Jul-2006 * Date Modified: 1. Impact A remote privileged user may create a TCP (tcp(7p)) "ACK storm" or "ACK flood" which can cause a networked system to run out of resources, creating a Denial of Service (DoS) condition. A TCP "ACK storm" can occur when a networked system sends a TCP packet which contains an incorrect sequence number to another networked system. The remote system will reply with a TCP ACK packet containing the expected sequence number and the originating system will send another packet with the incorrect sequence number. This exchange of ACK packets will continue indefinitely back and forth and thus create an "ACK storm". This is the expected behavior of the Internet Transmission Control Protocol (TCP) protocol. The TCP protocol specification is described in RFC 793 at: * http://www.ietf.org/rfc/rfc0793.txt The patches listed in Section Two below limit the number of replies a Solaris system will make to a TCP packet with an incorrect sequence number and thus protect against an "ACK storm". 2. Contributing Factors This issue can occur in the following releases: SPARC Platform * Solaris 8 without patch 116965-17 * Solaris 9 without patch 118305-07 * Solaris 10 without patch 118833-12 x86 Platform * Solaris 8 without patch 116966-16 * Solaris 9 without patch 117470-06 * Solaris 10 without patch 118855-10 3. Symptoms The system's performance will slow down if the described issue occurs, however, other systems on the network will not be affected. The snoop output will be similar to the following: --------------------------------------------------------------------------- - -------------- 5 0.00000 192.168.1.245 -> 192.168.1.58 TCP D=3071 S=8080 Fin Ack=2363 033 Seq=1558809380 Len=990 Win=8760 6 0.00000 192.168.1.245 -> 192.168.1.58 TCP D=3071 S=8080 Ack=2363 033 Seq=1558809380 Len=0 Win=8760 7 0.00000 192.168.1.58 -> 192.168.1.245 TCP D=8080 S=3071 Ack=1558 810371 Seq=2363033 Len=0 Win=7770 8 0.00000 192.168.1.245 -> 192.168.1.58 TCP D=3071 S=8080 Ack=2363 033 Seq=1558809380 Len=0 Win=8760 9 0.00000 192.168.1.58 -> 192.168.1.245 TCP D=8080 S=3071 Ack=1558 810371 Seq=2363033 Len=0 Win=7770 10 0.01000 192.168.1.245 -> 192.168.1.58 TCP D=3071 S=8080 Ack=2363 033 Seq=1558809380 Len=0 Win=8760 11 0.00000 192.168.1.58 -> 192.168.1.245 TCP D=8080 S=3071 Fin Ack=1558 810371 Seq=2363033 Len=0 Win=7770 12 0.00000 192.168.1.58 -> 192.168.1.245 TCP D=8080 S=3071 Ack=1558 810371 Seq=2363034 Len=0 Win=7770 13 0.00000 192.168.1.245 -> 192.168.1.58 TCP D=3071 S=8080 Ack=2363 033 Seq=1558809380 Len=0 Win=8760 ------------------------------------------------------------------ ----------------------- The systems performance will slow down if the described issue occurs, however, it will not effect other systems in the network. 4. Relief/Workaround There is no workaround. Please see the "Resolution" section below. 5. Resolution This issue is addressed in the following releases: SPARC Platform * Solaris 8 with patch 116965-17 or later * Solaris 9 with patch 118305-07 or later * Solaris 10 with patch 118833-12 or later x86 Platform * Solaris 8 with patch 116966-16 or later * Solaris 9 with patch 117470-06 or later * Solaris 10 with patch 118855-10 or later This Sun Alert notification is being provided to you on an "AS IS" basis. This Sun Alert notification may contain information provided by third parties. The issues described in this Sun Alert notification may or may not impact your system(s). Sun makes no representations, warranties, or guarantees as to the information contained herein. ANY AND ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING WITHOUT LIMITATION WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, OR NON-INFRINGEMENT, ARE HEREBY DISCLAIMED. BY ACCESSING THIS DOCUMENT YOU ACKNOWLEDGE THAT SUN SHALL IN NO EVENT BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, PUNITIVE, OR CONSEQUENTIAL DAMAGES THAT ARISE OUT OF YOUR USE OR FAILURE TO USE THE INFORMATION CONTAINED HEREIN. This Sun Alert notification contains Sun proprietary and confidential information. It is being provided to you pursuant to the provisions of your agreement to purchase services from Sun, or, if you do not have such an agreement, the Sun.com Terms of Use. This Sun Alert notification may only be used for the purposes contemplated by these agreements. Copyright 2000-2006 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, CA 95054 U.S.A. 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