🚀 go-pugleaf

Witam,

ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:15.tcp.asc

(...)

I.   Background

The Transmission Control Protocol (TCP) of the TCP/IP protocol suite
provides a connection-oriented, reliable, sequence-preserving data
stream service.  TCP timestamps are used to measure Round-Trip Time
and in the Protect Against Wrapped Sequences (PAWS) algorithm.  TCP
packets with the SYN flag set are used during setup of new TCP
connections.

II.  Problem Description

Two problems have been discovered in the FreeBSD TCP stack.

First, when a TCP packets containing a timestamp is received, inadequate
checking of sequence numbers is performed, allowing an attacker to
artificially increase the internal "recent" timestamp for a connection.

Second, a TCP packet with the SYN flag set is accepted for established
connections, allowing an attacker to overwrite certain TCP options.

III. Impact

Using either of the two problems an attacker with knowledge of the
local and remote IP and port numbers associated with a connection
can cause a denial of service situation by stalling the TCP connection.

The stalled TCP connection my be closed after some time by the other
host.

(...)

Pozdrawiam,

			Krzysztof Oledzki

-- 
Krzysztof Olędzki
e-mail address:		ole(a-t)ans(d-o-t)pl
Registered User:	Linux - 189200, BSD - 51140
Nick Handles:		KO60-RIPE, KO60-6BONE, KO581 (Network Solutions)