Common Vulnerabilities

Buffer overflow, command injections, cross-site scripting and SQL injections are the common types of vulnerabilities. Learn what they are, how it can be exploited, and strategies to prevent these types of attacks in your application.

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Buffer Overflow Attacks

What are they?

Like a flooding river, a buffer overflow has the potential to cause significant damage. To understand why, let’s begin at the source of the problem. In low-level languages that access and write memory, a part of this memory stays allocated for temporary data that needs to be saved during run-time. This part of memory is called a buffer. A buffer overflow happens when the data that needs to be saved exceeds the allocated memory space in the buffer.

What is an example of a buffer overflow?

As you can see in the image to the right, memory is made of different parts. Between the stack and the heap, there is a buffer area, which allows both to grow during run time. If we look at a stack in detail, we can see different sections:

• Function: the calling function written by the developer
• Parameters: the parameters needed by the function
• Return: it tells the program what to do after it has executed the function
• Basepointer: marks the start of a function stack frame
• Buffer: the allocated space for data

What types of Buffer Overflow are there?

This involves overflowing a buffer on the call stack, as described above.

Same as stack overflow, but it takes place in an open memory pool.

An arithmetic operation results in an integer that is too large for the integer type meant to store it.

Unicode characters are inserted into an input that expects ASCII characters.

How can you prevent Buffer Overflow attacks?

Avoid C/C++, these programming languages prone to buffer overflow

Address space layout randomization

Enhance the security of executable programs by detecting buffer overflows on stack-allocated variables

Mark memory regions as non-executable

Buffer Overflow-avoid standard library functions

Avoid standard library functions that are not bounds checked, such as gets, scanf and strcpy

Scan your code for buffer overflow vulnerabilities

Code Injection Attacks

What are they?

Code injection is a general term for a type of software vulnerability where unvalidated input is evaluated by an application. It is fairly common on web applications that rely on user input through forms that lack appropriate input/output data validation. This flaw can be exploited by attackers by injecting malicious code in the language of the application into it, which will then be executed by the server-side interpreter for that language.

Consequences of code injection can be dire:

• Data loss • Lack of accountability
• Data corruption • Denial of access

What types of Code Injections are there?

(file inclusion vulnerability)

Code Injection - format specifier injection

(format string attack)

How can you prevent Code Injection attacks?

Code Injection - validate and sanitize inputs

Validate and sanitize inputs – accept only a limited set of values

Use a SAST solution

Give the account the database calls run under only limited privileges

Code Injection - avoid vulnerable constructs

Avoid vulnerable evaluation constructs

Cross-site Scripting Attacks

What is Cross-site Scripting?

According to OWASP Top 10, XSS is the second-most prevalent issue found in the majority of web applications. By using XSS, attackers can bypass the Same Origin Policy (SOP) in a vulnerable application by entering malicious code which is mistakenly interpreted as user input. This can be done with technologies like VBScript, ActiveX, Flash and even CSS, but JavaScript attacks are the most common.

XSS differs from SQL because it does not target the database of web applications; it mostly limits itself to their front end.

These kinds of attack can be non-persistent, persistent and DOM-based. The consequences of XSS attacks can be very damaging, especially when combined with social engineering.

Websites or web interfaces can become corrupted and unsafe. Cookies and authentication information can be stolen, leading to identity theft. By hacking a vulnerable company website, attackers can gain control of the company’s computer clients.

What are some examples of Cross-site Scripting attacks?

How can you prevent Cross-site Scripting attacks?

Specify which tags are designed as “safe” in the HTML documents created by user inputs

Encode the data on output

Use Content Security Policy (CSP)

Use a Static Application Security Testing

The Dangers of SQL Injection Attacks

What are they?

From November 2017 – March 2019, 65% of web application attacks worldwide used SQL injection (SQLi). So it’s no surprise that injection attacks were named as the number one threat to web applications by the Open Web Application Security Project (OWASP).

Why are SQLi attacks so frequent?

Web forms that use SQL queries to retrieve data are very common, from login pages to search queries, online order forms, and more. These web forms are often connected to databases with potentially valuable information such as personal data and financial records.

By targeting web forms, attackers can bypass other types of security, such as firewalls and endpoint defenses. The knowledge needed to conduct an injection attack is readily available online.

Attackers use SQLi to extract data, such as passwords and credit card information. They can add, modify, or delete records in the database, perform database operations such as changing credentials or dropping entire tables, and more. Any database that uses Structured Query Language (SQL) is vulnerable to SQLi, including Microsoft SQL Server, Oracle, MySQL, PostgreSQL, and MongoDB.