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AUSCERT External Security Bulletin Redistribution
ESB-2006.0515 -- [Solaris]
Solaris Hosts are Vulnerable to a Denial of Service Induced by an Internet
Transmission Control Protocol (TCP) "ACK Storm"
28 July 2006
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AusCERT Security Bulletin Summary
---------------------------------
Product: Solaris
Publisher: Sun Microsystems
Operating System: Solaris 8,9,10
Impact: Denial of Service
Access: Remote/Unauthenticated
Original Bulletin:
http://sunsolve.sun.com/search/printfriendly.do?assetkey=1-26-102206-1
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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. All rights reserved
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