OpenSSH < 3.6.2 Reverse DNS Lookup Bypass

High Nessus Plugin ID 11712


The remote host has an application that is affected by DNS lookup bypass vulnerability.


According to its banner, the remote host appears to be running OpenSSH-portable version 3.6.1 or older.

There is a flaw in such version that could allow an attacker to bypass the access controls set by the administrator of this server.

OpenSSH features a mechanism that can restrict the list of hosts a given user can log from by specifying a pattern in the user key file (ie: * would let a user connect only from the local network).

However there is a flaw in the way OpenSSH does reverse DNS lookups.
If an attacker configures a DNS server to send a numeric IP address when a reverse lookup is performed, this mechanism could be circumvented.


Upgrade to OpenSSH 3.6.2 or later.

Plugin Details

Severity: High

ID: 11712

File Name: openssh_rev_dns_lookup_bypass.nasl

Version: $Revision: 1.21 $

Type: remote

Family: Misc.

Published: 2003/06/10

Modified: 2014/06/06

Dependencies: 10267

Risk Information

Risk Factor: High


Base Score: 7.5

Temporal Score: 6.5

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

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

Vulnerability Information

CPE: cpe:/a:openbsd:openssh

Exploit Available: true

Exploit Ease: No exploit is required

Vulnerability Publication Date: 2003/06/05

Reference Information

CVE: CVE-2003-0386

BID: 7831

OSVDB: 2112

CERT: 978316