IPSec replay attack
A vulnerability was found in the fast_ipsec stack that renders the IPSec anti-replay service ineffective under certain circumstances. If the upper layer protocol doesn't provide any anti-packet replay verification the system may be vulnerable to a replay attack.
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NetBSD Security Advisory 2006-011
Topic: IPSec replay attack
Version: NetBSD-current: source prior to March 23, 2006
NetBSD 3.0: affected
NetBSD 2.1: affected
NetBSD 2.0.*: affected
NetBSD 2.0: affected
Severity: Systems could be vulnerable to a replay attack
Fixed: NetBSD-current: March 23, 2006
NetBSD-3-0 branch: March 28, 2006
(3.0.1 will include the fix)
NetBSD-3 branch: March 28, 2006
NetBSD-2-1 branch: March 30, 2006
(2.1.1 will include the fix)
NetBSD-2-0 branch: March 30, 2006
(2.0.4 will include the fix)
NetBSD-2 branch: March 30, 2006
A vulnerability was found in the fast_ipsec(4) stack that renders the
IPSec anti-replay service ineffective under certain circumstances.
If the upper layer protocol doesn't provide any anti-packet replay
verification (for example, UDP) the system may be vulnerable to a
This vulnerability has been assigned CVE reference CVE-2006-0905.
The anti-replay service specifies an algorithm for preventing
injection of previously received packets from unknown parties
(the replay attack).
Due to a programming error in the fast_ipsec(4) stack, the Sequence
Number associated with a SA was not being updated, thus allowing
packets to bypass any sequence verification check.
Solutions and Workarounds
The default configuration of NetBSD does not ship with FAST_IPSEC enabled.
For all NetBSD versions, you need to obtain fixed kernel sources,
rebuild and install the new kernel, and reboot the system.
The fixed source may be obtained from the NetBSD CVS repository.
The following instructions briefly summarise how to upgrade your
kernel. In these instructions, replace:
ARCH with your architecture (from uname -m), and
KERNCONF with the name of your kernel configuration file.
To update from CVS, re-build, and re-install the kernel:
# cd src
# cvs update -d -P sys/netipsec/xform_esp.c
# ./build.sh kernel=KERNCONF
# mv /netbsd /netbsd.old
# cp sys/arch/ARCH/compile/obj/KERNCONF/netbsd /netbsd
# shutdown -r now
For more information on how to do this, see:
Pawel Jakub Dawidek is credited with the discovery of this issue
The FreeBSD Project for initial notification via FreeBSD-SA-06:11.ipsec
Rui Paulo for importing the fixes into NetBSD
2006-04-12 Initial release
Advisories may be updated as new information becomes available.
The most recent version of this advisory (PGP signed) can be found at
Information about NetBSD and NetBSD security can be found at
http://www.NetBSD.org/ and http://www.NetBSD.org/Security/.
Copyright 2006, The NetBSD Foundation, Inc. All Rights Reserved.
Redistribution permitted only in full, unmodified form.
$NetBSD: NetBSD-SA2006-011.txt,v 1.8 2006/04/12 22:53:07 adrianp Exp $
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