How does Remote Code Execution work?
This attack typically begins with discovering a vulnerability in a system. The attacker then crafts a payload to trigger unexpected behaviour, such as injecting malicious code.
Techniques like SQL injection, command injection, or cross-site scripting may be used to insert malicious code into user inputs that aren't properly validated.
The malicious payload, through a network connection, preys on systems. Once the system processes the payload, it triggers the underlying vulnerability, allowing the attacker to gain control. The attacker may escalate privileges to gain higher-level access and create a backdoor to extract sensitive data.
Remote Code execution can be achieved through the following:
Injection Vulnerability: Injection vulnerabilities occur due to poor input sanitisation. Input sanitisation occurs during authentication processes like sign-in, login, password resets, etc. If the proper methods or rules aren't followed, it can lead to injection vulnerabilities like SQL injection.
SQL injection is possible when a cyber-criminal crafts a query to fetch sensitive information such as usernames and passwords from an SQL database.
Deserialization Attack: Deserialization is the process of converting data, often stored in formats like JSON or XML, back into objects in memory. It is common to transfer or store data across parts of an application or between different applications.
If handled incorrectly, deserialization can introduce vulnerabilities. When data from an untrusted source is deserialized, attackers can corrupt data by injecting malicious code that grants the attacker administrative privileges or leads to remote code execution.
Buffer Overflow: Buffer overflows happen when the amount of data written to a buffer surpasses its allotted storage capacity, causing the extra data to spill into adjacent memory locations, potentially corrupting or overwriting the data in those locations.
File Inclusion Vulnerability: File inclusion vulnerabilities occur when a web application allows users to upload files to a server without proper sanitization or validation. If the attacker uploads a file with malicious code, the attacker gains access to the system, leading to remote code execution.
Impact of Remote Code Execution (RCE)
There are several impacts of remote code execution attacks, including:
Unauthorized Access: RCE vulnerabilities allow attackers to bypass authentication processes and gain unauthorized access to systems. This means an attacker can operate the system posing as a legitimate user, leading to service disruption or theft.
Information Disclosure: RCE vulnerability allows attackers to access sensitive information within the compromised system, such as user credentials, proprietary code, configuration files, etc. This exposure of data can have severe consequences regarding data privacy and security, such as;
Network Compromise: When an attacker gains access to a system, it can:
Exploit other systems within the network.
Escalate privileges and gain wider access.
Install backdoors or malware.
Access credentials or exfiltrate sensitive data.
Disrupt services or cause a shutdown.
A compromised network means that the integrity and confidentiality of the network cannot be trusted.
DDOS Attack: RCE vulnerability allows attackers to run arbitrary code on a remote system. Once the system is exploited, it can be used to launch other attacks, such as stealing data or installing malware. A compromised system can be used to carry out a Distributed Denial of Service (DDOS) attack, where malicious code is used to overwhelm a system resource to crash or make it unresponsive.
Ransomware: RCE enables cybercriminals to deploy ransomware to lock or encrypt files on compromised remote systems, making them inaccessible. The attacker would demand a ransom fee, usually in cryptocurrency, in exchange for the decryption key to re-enable access.
Examples of known Remote Code Execution Vulnerabilities are:
Log4j: This Apache Java-based logging library used in applications is a well-known Remote Code Execution Vulnerability (RCE). Older versions of Log4j had a critical FLAW (Log4Shell) that allowed attackers to remotely execute malware like cryptojackers on compromised servers.
Apache released patches to help address Log4shell and its related vulnerabilities, however, cyberthreats continue to exploit its flaws. If not patched correctly, or if the applications rely on dependencies that use Log4j, the system remains exposed to exploitation.
Shell Shock (CVE-2014-6271): This vulnerability was found in certain versions of the GNU Bourne Again Shell (Bash). It allows attackers to execute arbitrary commands on the affected system by injecting malicious code into environment variables.
This vulnerability affects systems that use Bash, including many servers that run Linux distributions.
EternalBlue: This is a Microsoft Windows exploit that allowed Microsoft devices to communicate with other Microsoft systems using file and print services. It contained a vulnerability discovered and allegedly exploited by the National Security Agency (NSA) to aid in anti-terrorism and counterintelligence operations.
However, Microsoft was not alerted in time to fix the vulnerability. When they were eventually alerted, they released patches for the exploit, but it was too late. Attackers had already begun exploiting it to send malicious data packets containing malware that spread to devices installed with vulnerable Microsoft software. They took advantage of the vulnerability and carried out attacks to spread malware.
Two incidents that highlight this vulnerability were the WannaCry ransomware attack and the NotPetya ransomware attack, both of which happened a few months apart in 2017.
WannaCry: WannaCry spread rapidly through the EternalBlue exploit, infecting around 230,000 Microsoft Windows machines in 150 different countries within a few hours.
NotPetya: The NotPetya ransomware attack used the EternalBlue exploit to propagate itself across Microsoft devices. The malware would install itself, encrypt data on the host device, and then demand a ransom of $300 in exchange for a decryption key
Preventive Measures Against Remote Code Execution
Key Practices to prevent remote code execution include the following:
Input Validation and Sanitization: These methods are crucial, and the application process must involve validating and sanitizing user inputs to block injection attacks.
Regular Update and Patching: Keep systems and software updated to address known vulnerabilities. Third-party dependencies can introduce flaws, which is why regular updates and maintenance can help reduce the chances of exploitation.
Follow Security Best Practices: Apply the principles of least privilege by ensuring users, applications, and processes have minimum access and permissions necessary to perform their assigned tasks. This reduces the risk of security breaches and errors. Additionally, using application firewalls helps minimise the attack surface.
Network Detection and Response Solution: Network detection and response solutions can monitor traffic and allow applications to detect and mitigate remote code execution vulnerabilities and other malicious activities, such as network scanning, unexpected user logins, and more.
Code Audits: Code audits are preventive security measures that involve looking for flaws or issues within the code base of an application before it goes live. Conducting thorough code audits can help identify and fix vulnerabilities before attackers have the chance to exploit them.
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