FreeBSD syncookies TCP Initial Sequence Number Weakness

BID:6920

Info

FreeBSD syncookies TCP Initial Sequence Number Weakness

Bugtraq ID: 6920
Class: Design Error
CVE:
Remote: Yes
Local: No
Published: Feb 24 2003 12:00AM
Updated: Feb 24 2003 12:00AM
Credit: This issue was reported in a FreeBSD Security Advisory.
Vulnerable: FreeBSD FreeBSD 5.0
FreeBSD FreeBSD 4.7
FreeBSD FreeBSD 4.6
FreeBSD FreeBSD 4.5
Not Vulnerable:

Discussion

FreeBSD syncookies TCP Initial Sequence Number Weakness

The FreeBSD implementation of syncookies are prone to brute force attacks. This is due to generated keys being 32 bits in length.

It is possible to generate valid ISN keys using a compromised syncookie. This may allow an attacker to spoof TCP connections that may be used to bypass IP-based access control lists.

Other attacks, including denial of service attacks, are also possible.

Exploit / POC

FreeBSD syncookies TCP Initial Sequence Number Weakness

Currently we are not aware of any exploits for this issue. If you feel we are in error or are aware of more recent information, please mail us at: [email protected] <mailto:[email protected]>.

Solution / Fix

FreeBSD syncookies TCP Initial Sequence Number Weakness

Solution:
FreeBSD has released an advisory. Users are advised to apply the included patches or to upgrade systems via CVS. Further information is available in the referenced advisory.

The following patches are available:


FreeBSD FreeBSD 4.6

FreeBSD FreeBSD 4.7

FreeBSD FreeBSD 5.0

References

FreeBSD syncookies TCP Initial Sequence Number Weakness

References:

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