OpenSSH < 3.6.2 Reverse DNS Lookup Bypass

high Nessus Plugin ID 11712

Synopsis

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

Description

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: *.mynetwork.com 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.

Solution

Upgrade to OpenSSH 3.6.2 or later.

Plugin Details

Severity: High

ID: 11712

File Name: openssh_rev_dns_lookup_bypass.nasl

Version: 1.23

Type: remote

Family: Misc.

Published: 6/10/2003

Updated: 3/27/2024

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 5.5

CVSS v2

Risk Factor: High

Base Score: 7.5

Temporal Score: 5.5

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

Vulnerability Information

CPE: cpe:/a:openbsd:openssh

Required KB Items: installed_sw/OpenSSH

Exploit Ease: No known exploits are available

Vulnerability Publication Date: 6/5/2003

Reference Information

CVE: CVE-2003-0386

BID: 7831

CERT: 978316