FreeBSD Security Advisory FreeBSD-SA-04:06.ipv6

Type securityvulns
Reporter Securityvulns
Modified 2004-03-30T00:00:00



============================================================================= FreeBSD-SA-04:06.ipv6 Security Advisory The FreeBSD Project

Topic: setsockopt(2) IPv6 sockets input validation error

Category: core Module: kernel Announced: 2004-03-29 Credits: Katsuhisa ABE, Colin Percival Affects: FreeBSD 5.2-RELEASE Corrected: 2004-03-29 14:01:33 UTC (RELENG_5_2, 5.2.1-RELEASE-p4) CVE Name: CAN-2004-0370 FreeBSD only: YES

For general information regarding FreeBSD Security Advisories, including descriptions of the fields above, security branches, and the following sections, please visit <URL:>.

I. Background

IPv6 is a new Internet Protocol, designed to replace (and avoid many of the problems with) the current Internet Protocol (version 4). FreeBSD uses the KAME Project IPv6 implementation.

Applications may manipulate the behavior of an IPv6 socket using the setsockopt(2) system call.

II. Problem Description

A programming error in the handling of some IPv6 socket options within the setsockopt(2) system call may result in memory locations being accessed without proper validation. While the problem originates in code from the KAME Project, it does not affect other operating systems.

III. Impact

It may be possible for a local attacker to read portions of kernel memory, resulting in disclosure of sensitive information. A local attacker can cause a system panic.

IV. Workaround

Do one of the following:

1) Disable IPv6 entirely by following these steps:

  • Remove or comment out any lines mentioning `INET6' from your kernel configuration file, and recompile your kernel as described in <URL:>.

  • Reboot your system.

2) If all untrusted users are confined within a jail(8), ensure that the security.jail.socket_unixiproute_only sysctl is set to 1 and verify that no IPv6 sockets are currently open:

sysctl security.jail.socket_unixiproute_only=1

sockstat -6

This will restrict jailed processes to creating UNIX domain, IPv4, and routing sockets, which are not vulnerable to this problem; note however that processes inside a jail may still be able to inherit IPv6 sockets from outside the jail, so this may not be sufficient for all systems.

V. Solution

Do one of the following:

1) Upgrade your vulnerable system to the RELENG_5_2 security branch dated after the correction date.

2) To patch your present system:

a) Download the relevant patch from the location below, and verify the detached PGP signature using your PGP utility.



b) Execute the following commands as root:

cd /usr/src

patch < /path/to/patch

c) Recompile the kernel as described in <URL:> and reboot the system.

d) Install updated kernel headers.

cd /usr/src/include

make install

VI. Correction details

The following list contains the revision numbers of each file that was corrected in FreeBSD.

Branch Revision Path

RELENG_5_2 src/UPDATING src/sys/netinet6/ip6_output.c src/sys/netinet/ip6.h src/sys/conf/

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