Security Vulnerability in the TCP Implementation of Solaris Systems May Allow a Denial of Service When Accepting New Connections While Undergoing a TCP "SYN Flood" Attack

Category
Security

Release Phase
Resolved

Bug Id
6402737

Date of Resolved Release
06-May-2008

Security Vulnerability in the TCP Implementation of Solaris Systems May Allow a Denial of Service When Accepting New Connections While Undergoing a TCP "SYN Flood" Attack

1. Impact

A security vulnerability in the TCP implementation of Solaris 8, 9 and 10 may allow a remote unprivileged user to cause a Solaris system which is undergoing a "TCP SYN" flood condition to be slow to accept new network connections. Such network connections may time out without establishing a connection. This would lead to a Denial of Service (DoS) to the network services provided by that system. In addition, a uniprocessor system may also experience overall slowdown due to high CPU usage, resulting in a Denial of Service to the system as a whole.

2. Contributing Factors

This issue can occur in the following releases:

SPARC Platform

Solaris 8 without patch 116965-33
Solaris 9 without patch 114344-35
Solaris 10 without patch 119998-01

x86 Platform

Solaris 8 without patch 116966-32
Solaris 9 without patch 119435-23
Solaris 10 without patch 119999-01

Note: This issue affects hosts which have a value for the ndd(1M) tunable 'tcp_conn_req_max_q0' which is considerably higher than the default value of 1024. The higher the value, the greater the impact of this issue if it is exploited on a host. While a value close to or less than 1024 does not make the system immune to a Denial of Service, it decreases the impact of a DoS on the system.

To determine the value of the 'tcp_conn_req_max_q0' tunable, the following command can be used:

    $ ndd -get /dev/tcp tcp_conn_req_max_q0
    1024

3. Symptoms

If this issue is exploited, the following message may be seen on the console:

    WARNING: High TCP connect timeout rate! 
    System (port <port number>) may be under a SYN flood attack

4. Workaround

To work around the described issue, make sure the value of the ndd(1M) tunable 'tcp_conn_req_max_q0' for TCP is not much higher than the default of 1024, using commands such as the following:

    $ ndd -get /dev/tcp tcp_conn_req_max_q0 
    4000
    $ ndd -set /dev/tcp tcp_conn_req_max_q0 1024
    $ ndd -get /dev/tcp tcp_conn_req_max_q0 
    1024

5. Resolution

This issue is addressed in the following releases:

SPARC Platform

Solaris 8 with patch116965-33 or later
Solaris 9 with patch 114344-35 or later
Solaris 10 with patch 119998-01 or later

x86 Platform

Solaris 8 with patch 116966-32 or later
Solaris 9 with patch 119435-23 or later
Solaris 10 with patch 119999-01 or later

Note: There are additional Solaris 8 and 9 patches which list 6402737 in their README, however these patches are not required to address the issue described in this Sun Alert. These additional patches deliver an updated kernel debugger (kadb(1M)). The patch-IDs are:

SPARC Platform

Solaris 8 patch 117350-54 or later
Solaris 9 patch 122300-25 or later

x86 Platform

Solaris 8 patch 117351-54 or later
Solaris 9 patch 122301-25 or later

For more information on Security Sun Alerts, see 1009886.1.

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 2000-2008 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, CA 95054 U.S.A. All rights reserved.

Modification History
30-Jul-2008: Updated "Note" in Contributing Factors for clarification

Product
Solaris 8 Operating System
Solaris 9 Operating System
Solaris 10 Operating System

References

116965-33
114344-35
119998-01
116966-32
119435-23
119999-01
117350-54
117351-54
122300-25
122301-25

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