OpenSSH < 3.6.2 Reverse DNS Lookup Bypass

high Nessus Plugin ID 11712

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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

Detections

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