OpenSSH LoginGraceTime / MaxStartups DoS

Medium Nessus Plugin ID 67140

Synopsis

The remote SSH service is susceptible to a remote denial of service attack.

Description

According to its banner, a version of OpenSSH earlier than version 6.2 is listening on this port. The default configuration of OpenSSH installs before 6.2 could allow a remote attacker to bypass the LoginGraceTime and MaxStartups thresholds by periodically making a large number of new TCP connections and thereby prevent legitimate users from gaining access to the service.

Note that this plugin has not tried to exploit the issue or detect whether the remote service uses a vulnerable configuration. Instead, it has simply checked the version of OpenSSH running on the remote host.

Solution

Upgrade to OpenSSH 6.2 and review the associated server configuration settings.

See Also

https://www.openwall.com/lists/oss-security/2013/02/06/5

http://openssh.org/txt/release-6.2

https://tools.cisco.com/security/center/viewAlert.x?alertId=28883

Plugin Details

Severity: Medium

ID: 67140

File Name: openssh_logingrace_dos.nasl

Version: 1.7

Type: remote

Published: 2013/07/03

Modified: 2018/11/15

Dependencies: 10267

Risk Information

Risk Factor: Medium

CVSS v2.0

Base Score: 5

Temporal Score: 3.7

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

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

Vulnerability Information

CPE: cpe:/a:openbsd:openssh

Required KB Items: Settings/ParanoidReport

Exploit Available: false

Exploit Ease: No known exploits are available

Patch Publication Date: 2013/03/22

Vulnerability Publication Date: 2013/02/06

Reference Information

CVE: CVE-2010-5107

BID: 58162