Linux Kernel TCP Sequence Number Generation Security Weakness

Medium Nessus Plugin ID 56283


It may be possible to predict TCP/IP Initial Sequence Numbers for the remote host.


The Linux kernel is prone to a security weakness related to TCP sequence number generation. Attackers can exploit this issue to inject arbitrary packets into TCP sessions using a brute-force attack.

An attacker may use this vulnerability to create a denial of service condition or a man-in-the-middle attack.

Note that this plugin may fire as a result of a network device (such as a load balancer, VPN, IPS, transparent proxy, etc.) that is vulnerable and that re-writes TCP sequence numbers, rather than the host itself being vulnerable.


Contact the OS vendor for a Linux kernel update / patch.

See Also

Plugin Details

Severity: Medium

ID: 56283

File Name: linux_isn.nasl

Version: $Revision: 1.14 $

Type: remote

Family: General

Published: 2011/09/23

Modified: 2014/05/26

Risk Information

Risk Factor: Medium


Base Score: 6.8

Temporal Score: 5.9

Vector: CVSS2#AV:N/AC:M/Au:N/C:P/I:P/A:P

Temporal Vector: CVSS2#E:ND/RL:OF/RC:C

Vulnerability Information

Required KB Items: Settings/ParanoidReport

Exploit Available: true

Exploit Ease: Exploits are available

Vulnerability Publication Date: 2011/08/23

Reference Information

CVE: CVE-2011-3188

BID: 49289

OSVDB: 75716