FreeBSD < 10.3-RELEASE-p21 / 11.0 < 11.0-RELEASE-p12 / 11.1 < 11.1-RELEASE-p1 OpenSSH Password Length DoS (FreeBSD-SA-17:06.openssh)

high Nessus Plugin ID 102917

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Synopsis

The remote FreeBSD host is missing a security-related update.

Description

The version of the FreeBSD kernel running on the remote host is prior to 10.3-RELEASE-p21, 11.0 prior to 11.0-RELEASE-p12, or 11.1 prior to 11.1-RELEASE-p1. It, therefore, affected by a flaw in built-in password authentication in OpenSSH. An unauthenticated, remote attacker can exploit this issue by sending very long passwords when PasswordAuthentication is enabled by the system administrator, resulting in a denial of service condition.

Note that this issue only affects hosts with PasswordAuthentication enabled in /etc/ssh/sshd_config (the default FreeBSD configuration).

You may workaround this issue by disabling PasswordAuthentication and restarting sshd.

Solution

Upgrade to FreeBSD version 10.3-RELEASE-p21 / 11.0-RELEASE-p12 / 11.1-RELEASE-p1 or later. Alternatively, apply the workaround referenced in the advisory to disable PasswordAuthentication.

Plugin Details

Severity: High

ID: 102917

File Name: freebsd_sa-17-06_openssh.nasl

Version: 1.3

Type: local

Family: FreeBSD Local Security Checks

Published: 9/1/2017

Updated: 4/10/2019

Configuration: Enable paranoid mode

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

CVSS v2

Risk Factor: High

Base Score: 7.8

Temporal Score: 6.1

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

CVSS v3

Risk Factor: High

Base Score: 7.5

Temporal Score: 6.7

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

Temporal Vector: CVSS:3.0/E:P/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:freebsd:freebsd

Required KB Items: Host/local_checks_enabled, Host/FreeBSD/release, Host/FreeBSD/pkg_info, Settings/ParanoidReport

Exploit Available: true

Exploit Ease: Exploits are available

Patch Publication Date: 8/10/2017

Vulnerability Publication Date: 8/10/2017

Reference Information

CVE: CVE-2016-6515

BID: 92212

Detections

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