OpenSSH < 3.6.2 Reverse DNS Lookup Bypass

high Nessus Network Monitor Plugin ID 701171


The remote OpenSSH server is affected by a DNS lookup bypass vulnerability.


According to its banner, the remote host appears to be running OpenSSH-portable version 3.6.1 or older and is affected by 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 version 3.6.2 or later.

See Also

Plugin Details

Severity: High

ID: 701171

Family: SSH

Published: 8/21/2019

Updated: 8/21/2019

Nessus ID: 11712

Risk Information


Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

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

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


Risk Factor: High

Base Score: 7.3

Temporal Score: 6.4

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

Temporal Vector: E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:openbsd:openssh

Patch Publication Date: 6/5/2003

Vulnerability Publication Date: 6/5/2003

Reference Information

CVE: CVE-2003-0386

BID: 7831