CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Description

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 lead to a vulnerability in environments in which the attacker does not have direct access to the operating system, such as in web applications. Alternately, if the weakness occurs in a privileged program, it could allow the attacker to specify commands that normally would not be accessible, or to call alternate commands with privileges that the attacker does not have. The problem is exacerbated if the compromised process does not follow the principle of least privilege, because the attacker-controlled commands may run with special system privileges that increases the amount of damage. There are at least two subtypes of OS command injection: From a weakness standpoint, these variants represent distinct programmer errors. In the first variant, the programmer clearly intends that input from untrusted parties will be part of the arguments in the command to be executed. In the second variant, the programmer does not intend for the command to be accessible to any untrusted party, but the programmer probably has not accounted for alternate ways in which malicious attackers can provide input.

Potential Impact

Demonstrative Examples

$userName = $_POST["user"];$command = 'ls -l /home/' . $userName;system($command);

;rm -rf /

ls -l /home/;rm -rf /

int main(int argc, char** argv) {char cmd[CMD_MAX] = "/usr/bin/cat ";strcat(cmd, argv[1]);system(cmd);}

use CGI qw(:standard);$name = param('name');$nslookup = "/path/to/nslookup";print header;if (open($fh, "$nslookup $name|")) {while (<$fh>) {print escapeHTML($_);print "<br>\n";}close($fh);}

cwe.mitre.org%20%3B%20/bin/ls%20-l

/path/to/nslookup cwe.mitre.org ; /bin/ls -l

String script = System.getProperty("SCRIPTNAME");if (script != null)System.exec(script);

Mitigations & Prevention

Detection Methods

• Automated Static Analysis — This weakness can often be detected using automated static analysis tools. Many modern tools use data flow analysis or constraint-based techniques to minimize the number of false positives. Automated static analysis might not be able to recognize when proper input validation is b
• Automated Dynamic Analysis Moderate — 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,
• Manual Static Analysis High — 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.
• Automated Static Analysis - Binary or Bytecode High — According to SOAR [REF-1479], the following detection techniques may be useful:
• Dynamic Analysis with Automated Results Interpretation SOAR Partial — According to SOAR [REF-1479], the following detection techniques may be useful:
• Dynamic Analysis with Manual Results Interpretation SOAR Partial — According to SOAR [REF-1479], the following detection techniques may be useful:

Real-World CVE Examples

Showing 15 of 19 observed examples.

Related Weaknesses

Taxonomy Mappings

• PLOVER: — OS Command Injection
• OWASP Top Ten 2007: A3 — Malicious File Execution
• OWASP Top Ten 2004: A6 — Injection Flaws
• CERT C Secure Coding: ENV03-C — Sanitize the environment when invoking external programs
• CERT C Secure Coding: ENV33-C — Do not call system()
• CERT C Secure Coding: STR02-C — Sanitize data passed to complex subsystems
• WASC: 31 — OS Commanding
• The CERT Oracle Secure Coding Standard for Java (2011): IDS07-J — Do not pass untrusted, unsanitized data to the Runtime.exec() method
• Software Fault Patterns: SFP24 — Tainted input to command
• OMG ASCSM: ASCSM-CWE-78 —