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Test ID:1.3.6.1.4.1.25623.1.0.52634
Category:FreeBSD Local Security Checks
Title:FreeBSD Security Advisory (FreeBSD-SA-02:20.syncache.asc)
Summary:The remote host is missing an update to the system; as announced in the referenced advisory FreeBSD-SA-02:20.syncache.asc
Description:Summary:
The remote host is missing an update to the system
as announced in the referenced advisory FreeBSD-SA-02:20.syncache.asc

Vulnerability Insight:
The SYN cache (syncache) and SYN cookie mechanism (syncookie) are
features of the TCP/IP stack intended to improve resistance to a class
of denial of service attacks known as SYN floods.

Two related problems with syncache were triggered when syncookies were
implemented.

1) When a SYN was accepted via a syncookie, it used an uninitialized
pointer to find the TCP options for the new socket. This pointer may
be a null pointer, which will cause the machine to crash.

2) A syncache entry is created when a SYN arrives on a listen socket.
If the application which created the listen socket was killed and
restarted --- and therefore recreated the listen socket with a
different inpcb --- an ACK (or duplicate SYN) which later arrived and
matched the existing syncache entry would cause a reference to the old
inpcb pointer. Depending on the pointer's contents, this might result
in a system crash.

Because syncache/syncookies support was added prior to the release of
FreeBSD 4.5-RELEASE, no other releases are affected.

Solution:
Upgrade your system to the appropriate stable release
or security branch dated after the correction date.

CVSS Score:
5.0

CVSS Vector:
AV:N/AC:L/Au:N/C:N/I:N/A:P

Cross-Ref: Common Vulnerability Exposure (CVE) ID: CVE-2002-0518
BugTraq ID: 4524
http://www.securityfocus.com/bid/4524
FreeBSD Security Advisory: FreeBSD-SA-02:20
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-02:20.syncache.asc
http://www.osvdb.org/6046
http://www.iss.net/security_center/static/8875.php
http://www.iss.net/security_center/static/8873.php
CopyrightCopyright (C) 2008 E-Soft Inc.

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