8.8 CVE-2017-6334

CISA Kev Catalog RCE Injection SQL Used by Malware Exploit

dnslookup.cgi on NETGEAR DGN2200 devices with firmware through 10.0.0.50 allows remote authenticated users to execute arbitrary OS commands via shell metacharacters in the host_name field of an HTTP POST request, a different vulnerability than CVE-2017-6077.
https://nvd.nist.gov/vuln/detail/CVE-2017-6334

Categories

CWE-78 : Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')
The product constructs all or part of an OS command using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the intended OS command when it is sent to a downstream component. This weakness can be detected using dynamic tools and techniques that interact with the product using large test suites with many diverse inputs, such as fuzz testing (fuzzing), robustness testing, and fault injection. The product's operation may slow down, but it should not become unstable, crash, or generate incorrect results. Since this weakness does not typically appear frequently within a single software package, manual white box techniques may be able to provide sufficient code coverage and reduction of false positives if all potentially-vulnerable operations can be assessed within limited time constraints. If at all possible, use library calls rather than external processes to recreate the desired functionality. For any data that will be used to generate a command to be executed, keep as much of that data out of external control as possible. For example, in web applications, this may require storing the data locally in the session's state instead of sending it out to the client in a hidden form field. For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks entirely. Then, these modified values would be submitted to the server. While it is risky to use dynamically-generated query strings, code, or commands that mix control and data together, sometimes it may be unavoidable. Properly quote arguments and escape any special characters within those arguments. The most conservative approach is to escape or filter all characters that do not pass an extremely strict allowlist (such as everything that is not alphanumeric or white space). If some special characters are still needed, such as white space, wrap each argument in quotes after the escaping/filtering step. Be careful of argument injection (CWE-88). If the program to be executed allows arguments to be specified within an input file or from standard input, then consider using that mode to pass arguments instead of the command line. When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs. Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184). Run the code in an environment that performs automatic taint propagation and prevents any command execution that uses tainted variables, such as Perl's "-T" switch. This will force the program to perform validation steps that remove the taint, although you must be careful to correctly validate your inputs so that you do not accidentally mark dangerous inputs as untainted (see CWE-183 and CWE-184). Use runtime policy enforcement to create an allowlist of allowable commands, then prevent use of any command that does not appear in the allowlist. Technologies such as AppArmor are available to do this. Use an application firewall that can detect attacks against this weakness. It can be beneficial in cases in which the code cannot be fixed (because it is controlled by a third party), as an emergency prevention measure while more comprehensive software assurance measures are applied, or to provide defense in depth. Run your code using the lowest privileges that are required to accomplish the necessary tasks [REF-76]. If possible, create isolated accounts with limited privileges that are only used for a single task. That way, a successful attack will not immediately give the attacker access to the rest of the software or its environment. For example, database applications rarely need to run as the database administrator, especially in day-to-day operations. When using PHP, configure the application so that it does not use register_globals. During implementation, develop the application so that it does not rely on this feature, but be wary of implementing a register_globals emulation that is subject to weaknesses such as CWE-95, CWE-621, and similar issues. OS command injection in Wi-Fi router, as exploited in the wild per CISA KEV. Template functionality in network configuration management tool allows OS command injection, as exploited in the wild per CISA KEV. Chain: improper input validation (CWE-20) in username parameter, leading to OS command injection (CWE-78), as exploited in the wild per CISA KEV. Canonical example of OS command injection. CGI program does not neutralize "|" metacharacter when invoking a phonebook program. Language interpreter's mail function accepts another argument that is concatenated to a string used in a dangerous popen() call. Since there is no neutralization of this argument, both OS Command Injection (CWE-78) and Argument Injection (CWE-88) are possible. Web server allows command execution using "|" (pipe) character. FTP client does not filter "|" from filenames returned by the server, allowing for OS command injection. Shell metacharacters in a filename in a ZIP archive Shell metacharacters in a telnet:// link are not properly handled when the launching application processes the link. OS command injection through environment variable. OS command injection through https:// URLs Chain: incomplete denylist for OS command injection Product allows remote users to execute arbitrary commands by creating a file whose pathname contains shell metacharacters.

References

cve@mitre.org Exploit

http://www.securityfocus.com/bid/96463 Broken Link Third Party Advisory VDB Entry
https://www.exploit-db.com/exploits/41459/ Exploit Third Party Advisory VDB Entry
https://www.exploit-db.com/exploits/41472/ Exploit Third Party Advisory VDB Entry
https://www.exploit-db.com/exploits/42257/ Exploit Third Party Advisory VDB Entry

CPE

cpe	start	end
Configuration 1
AND
cpe:2.3:o:netgear:dgn2200_series_firmware::::::::		<= 10.0.0.50
Running on/with
cpe:2.3:h:netgear:dgn2200v1:-:::::::*
cpe:2.3:h:netgear:dgn2200v2:-:::::::*
cpe:2.3:h:netgear:dgn2200v3:-:::::::*
cpe:2.3:h:netgear:dgn2200v4:-:::::::*

REMEDIATION

EXPLOITS

Exploit-db.com

id	description	date
42257	Netgear DGN2200 - 'dnslookup.cgi' Command Injection (Metasploit)	2017-06-26
41459	Netgear DGN2200v1/v2/v3/v4 - 'dnslookup.cgi' Remote Command Execution	2017-02-27

POC Github

Url
No known exploits

Other Nist (github, ...)

Url
https://www.exploit-db.com/exploits/41459/
https://www.exploit-db.com/exploits/41472/
https://www.exploit-db.com/exploits/42257/

CAPEC

Common Attack Pattern Enumerations and Classifications

id	description	severity
108	Command Line Execution through SQL Injection An attacker uses standard SQL injection methods to inject data into the command line for execution. This could be done directly through misuse of directives such as MSSQL_xp_cmdshell or indirectly through injection of data into the database that would be interpreted as shell commands. Sometime later, an unscrupulous backend application (or could be part of the functionality of the same application) fetches the injected data stored in the database and uses this data as command line arguments without performing proper validation. The malicious data escapes that data plane by spawning new commands to be executed on the host. [Probe for SQL Injection vulnerability] The attacker injects SQL syntax into user-controllable data inputs to search unfiltered execution of the SQL syntax in a query. [Achieve arbitrary command execution through SQL Injection with the MSSQL_xp_cmdshell directive] The attacker leverages a SQL Injection attack to inject shell code to be executed by leveraging the xp_cmdshell directive. [Inject malicious data in the database] Leverage SQL injection to inject data in the database that could later be used to achieve command injection if ever used as a command line argument [Trigger command line execution with injected arguments] The attacker causes execution of command line functionality which leverages previously injected database content as arguments.	Very High
15	Command Delimiters An attack of this type exploits a programs' vulnerabilities that allows an attacker's commands to be concatenated onto a legitimate command with the intent of targeting other resources such as the file system or database. The system that uses a filter or denylist input validation, as opposed to allowlist validation is vulnerable to an attacker who predicts delimiters (or combinations of delimiters) not present in the filter or denylist. As with other injection attacks, the attacker uses the command delimiter payload as an entry point to tunnel through the application and activate additional attacks through SQL queries, shell commands, network scanning, and so on. [Assess Target Runtime Environment] In situations where the runtime environment is not implicitly known, the attacker makes connections to the target system and tries to determine the system's runtime environment. Knowing the environment is vital to choosing the correct delimiters. [Survey the Application] The attacker surveys the target application, possibly as a valid and authenticated user [Attempt delimiters in inputs] The attacker systematically attempts variations of delimiters on known inputs, observing the application's response each time. [Use malicious command delimiters] The attacker uses combinations of payload and carefully placed command delimiters to attack the software.	High
43	Exploiting Multiple Input Interpretation Layers An attacker supplies the target software with input data that contains sequences of special characters designed to bypass input validation logic. This exploit relies on the target making multiples passes over the input data and processing a "layer" of special characters with each pass. In this manner, the attacker can disguise input that would otherwise be rejected as invalid by concealing it with layers of special/escape characters that are stripped off by subsequent processing steps. The goal is to first discover cases where the input validation layer executes before one or more parsing layers. That is, user input may go through the following logic in an application: <parser1> --> <input validator> --> <parser2>. In such cases, the attacker will need to provide input that will pass through the input validator, but after passing through parser2, will be converted into something that the input validator was supposed to stop. [Determine application/system inputs where bypassing input validation is desired] The attacker first needs to determine all of the application's/system's inputs where input validation is being performed and where they want to bypass it. [Determine which character encodings are accepted by the application/system] The attacker then needs to provide various character encodings to the application/system and determine which ones are accepted. The attacker will need to observe the application's/system's response to the encoded data to determine whether the data was interpreted properly. [Combine multiple encodings accepted by the application.] The attacker now combines encodings accepted by the application. The attacker may combine different encodings or apply the same encoding multiple times. [Leverage ability to bypass input validation] Attacker leverages their ability to bypass input validation to gain unauthorized access to system. There are many attacks possible, and a few examples are mentioned here.	High
6	Argument Injection An attacker changes the behavior or state of a targeted application through injecting data or command syntax through the targets use of non-validated and non-filtered arguments of exposed services or methods. [Discovery of potential injection vectors] Using an automated tool or manual discovery, the attacker identifies services or methods with arguments that could potentially be used as injection vectors (OS, API, SQL procedures, etc.). [1. Attempt variations on argument content] Possibly using an automated tool, the attacker will perform injection variations of the arguments. [Abuse of the application] The attacker injects specific syntax into a particular argument in order to generate a specific malicious effect in the targeted application.	High
88	OS Command Injection In this type of an attack, an adversary injects operating system commands into existing application functions. An application that uses untrusted input to build command strings is vulnerable. An adversary can leverage OS command injection in an application to elevate privileges, execute arbitrary commands and compromise the underlying operating system. [Identify inputs for OS commands] The attacker determines user controllable input that gets passed as part of a command to the underlying operating system. [Survey the Application] The attacker surveys the target application, possibly as a valid and authenticated user [Vary inputs, looking for malicious results.] Depending on whether the application being exploited is a remote or local one the attacker crafts the appropriate malicious input, containing OS commands, to be passed to the application [Execute malicious commands] The attacker may steal information, install a back door access mechanism, elevate privileges or compromise the system in some other way.	High

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