In today’s increasingly connected world, web applications are like the doors and windows of your business. They allow data to flow in and out, enable communication, and make operations more efficient. They are vital for an online business to remain competitive.
However, just as a building with poorly secured doors or windows, invites intruders, a web application with software vulnerabilities leaves your business exposed to cyberattacks. One such vulnerability, often overlooked but incredibly dangerous, is command injection. Like leaving a key under the doormat, command injection provides attackers with an easy way to sneak into your system and take control.
This blog post explores what command injection is, why it’s a significant threat to businesses, and how it compares to other web application vulnerabilities. It also explores how to protect your digital doors and windows from malicious attackers, who are constantly looking to exploit weaknesses in web applications.
Why are web applications not 100% secure?
Even an apparently simple web application is made of fairly complex code. This code cannot be guaranteed to be error free, and the only accepted way to control errors if for thorough testing to take place. This should be done by the vendors, but errors still slip through. Once identified, these errors are published and known as vulnerabilities which must be patched asap (i.e. within 14 days). Otherwise, they can be exploited by hackers.
What is Command Injection?
Put simply, command injection occurs when attackers manage to insert and execute unauthorized system commands by exploiting vulnerabilities in a web application. When user inputs are not properly sanitized or validated, attackers can hijack the application's communication with the underlying operating system, turning a simple input field into a gateway for malicious activity.
For instance, imagine an online form that asks for a filename to be processed. If, through poor coding, this form isn’t secure, an attacker could insert commands into the input instead of just the filename. This could trick the server into executing commands that weren’t part of the intended function, allowing the attacker to manipulate the system in dangerous ways.
How Command Injection Works
Command injection is like handing over the control of your computer to a stranger without realizing it. Normally, your web application should be in full control of what commands get executed. However, when it’s vulnerable to command injection, it’s as though you’ve accidentally allowed the attacker to grab the keyboard and type commands directly into your server’s terminal.
Example 1: if a web application allows the passing of user input into a system command (like listing files in a directory) without properly sanitizing it, an attacker could include additional malicious commands along with their input. If they successfully inject a command like `; rm -rf /`, it would delete files from the server—potentially leading to devastating consequences for your business.
Example 2: imagine you’re using a website that lets you check if a certain website is online by typing its name into a search bar. Normally, you would type something like "example.com", and the website would send a request to check if that site is working.
Fine, but if the website’s system isn't properly secured, a hacker could type something malicious into the search like:
example.com; delete all files
Because the website doesn’t stop the extra command, it would not only check if "example.com" is online, but also follow the hacker's second instruction to delete all files on the server. This could cause major damage, such as wiping out all data from the website's server.
Why Command Injection is particularly dangerous for Businesses
1. Data Breaches: Attackers can steal sensitive business and customer data, leading to costly breaches and reputational damage.
2. System Takeover: Command injection allows attackers to gain control over critical systems, potentially bringing business operations to a standstill.
3. Regulatory Penalties: Failing to protect against vulnerabilities like command injection could lead to violations of regulations such as GDPR, resulting in heavy fines.
4. Erosion of Trust: Customers and partners expect their data to be secure. A breach stemming from a vulnerability like command injection can erode trust and loyalty, which may be difficult to rebuild.
How to Mitigate Command Injection Risks
To protect against command injection, businesses must adopt a defence-in-depth approach.
1. Quite simply, only use web applications on (e.g.) an Apple or Google approved list (reputable software vendors do all they can to get their apps onto such a list). Any application not on such a list is more likely to have vulnerabilities including allowing command line injection at an input box through poor coding or a software bug.
2. Use principle of Least Privilege: run applications with the minimum necessary system privileges (i.e. not as administrator!) to limit the potential damage from a command injection attack.
3. Conduct Regular Security Audits: routinely run scans with reputable vulnerability testing tools to identify vulnerabilities. Once identified, a vulnerability can be fixed promptly, preventing attack.
Any web apps that do not use input validation [using secure functions and libraries that prevent user input from being directly passed into system commands] should not be used. Such applications would not be on any reputable web app list anyway!
Command injection also includes a more specific vulnerability: SQL Injection. Here, the malicious user input, specifically targets an SQL-based database by injecting harmful SQL queries. The difference between SQL and Command injection is that the latter manipulates system commands at the operating system level, making it broader in scope and potentially even more damaging.
Other Web Vulnerabilities to Consider
Online activity also has a client (user) end that can be exploited. This also needs careful treatment at the server end to prevent the 3rd party intervention…
- Cross-Site Scripting (XSS) involves injecting malicious scripts into web pages as they are created at the server end and sent across the Internet to be viewed by users. XSS directly affects the client-side (the user’s browser), while command injection directly affects the organisations server-side system.
- Cross-Site Request Forgery (CSRF) tricks users into performing unwanted actions on a web application that the server end has already authenticated. Like XSS, CSRF also therefore exploits the trust a web application has at the user browser end.
Conclusion
Command injection is a serious threat that businesses must be aware of and defend against. Like leaving your business’s doors and windows unlocked, a vulnerability in your web application can invite attackers to wreak havoc, stealing data, disrupting operations, and compromising your business’s reputation. By understanding how command injection works and implementing strong security measures, businesses can prevent these attacks and protect their digital infrastructure from costly breaches.
Command injection is just one of many potential vulnerabilities, but it stands out due to the direct control it can give attackers over your system. Prioritizing security practices such as input validation, secure coding, and regular security audits will help mitigate this risk and ensure your business remains protected.
Useful links:
NCSC (National Cyber Security Centre) offers comprehensive information about various security vulnerabilities, including command injection, and practical guidance on how to secure your systems. Their site is an excellent resource for up-to-date cybersecurity advisories and news: https://www.ncsc.gov.uk
Article on command Injection:
Regola blog on SQL injection:
Regola blog on Cross-Site Scripting:
Regola blog on Cross-Site Request Forgery:
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