Rapid7 Vulnerability & Exploit Database

Predictable TCP Initial Sequence Number

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Predictable TCP Initial Sequence Number

Severity
8
CVSS
(AV:N/AC:L/Au:N/C:P/I:P/A:P)
Published
01/01/1995
Created
07/25/2018
Added
07/16/2009
Modified
02/13/2015

Description

Some TCP/IP stack implementations use non-random increments for initial sequence numbers (ISN). This could allow remote attackers to perform spoofing and session hijacking.

Nmap ranks the sequence predictability (SP) score as follows:

  • SP < 3: Trivial Joke
  • SP < 6: Easy
  • SP < 11: Medium
  • SP < 12: Formidable
  • SP < 16: Worthy Challenge
  • SP >= 16 : Good Luck!

Solution(s)

  • fix-tcp-predictable-isn

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