Remote Code Execution (RCE): How It Works and 8 Defensive Strategies

What Is Remote Code Execution (RCE)? 

Remote code execution (RCE) is a critical security vulnerability that allows an attacker to execute arbitrary code on a remote system. This type of vulnerability can be exploited to take control over an affected system. 

RCE can occur due to flaws in software that allow malicious code to be executed in an environment where it should not be permitted. It's a significant threat because it allows attackers to manipulate or completely take over computer systems.

RCE vulnerabilities enable attackers to bypass security measures and execute unauthorized tasks. Through RCE, attackers can launch further attacks within a network, steal sensitive data, or cause system disruptions. These attacks enable exploitation at varying levels, from accessing data to full system compromise, often without user detection until significant damage is done.

This is part of a series of articles about application security vulnerabilities.

Impact of Remote Code Execution Attacks 

The impact of remote code execution (RCE) attacks can range from minor disruptions to catastrophic system breaches, depending on the scope of the vulnerability and the attacker’s objectives. At their worst, RCE attacks grant attackers complete control over a target system, allowing them to perform any operation the compromised system is capable of.

Common impacts of RCE attacks include:

1. System compromise: Attackers can gain administrative or root-level access, enabling them to alter configurations, disable security controls, and install additional malware. This level of control can lead to further exploitation, such as creating backdoors for ongoing access.
2. Data breach and theft: RCE can be used to extract sensitive information, including personally identifiable information (PII), intellectual property, and financial data. Such breaches can lead to reputational damage, legal consequences, and financial losses for organizations.
3. Disruption of services: Attackers may exploit RCE to disrupt operations by shutting down systems, corrupting data, or launching distributed denial-of-service (DDoS) attacks. Such disruptions can significantly affect business continuity and revenue.
4. Network propagation: Exploiting RCE on one system can allow attackers to pivot and target other devices within a network. This lateral movement can expand the scope of the attack, affecting multiple systems and increasing recovery costs.
5. Ransomware deployment: RCE vulnerabilities are often exploited to install ransomware, encrypting critical files and demanding payment for their release. This can paralyze operations and lead to significant financial and reputational repercussions.

How Does Remote Code Execution Work?

Remote code execution attacks exploit vulnerabilities that allow attackers to inject and execute malicious code on a target system. These vulnerabilities can exist in application logic, server configurations, or underlying system components.

1. Identifying a vulnerability: Attackers begin by identifying exploitable flaws, such as vulnerable third-party libraries, unvalidated inputs, insecure deserialization, or buffer overflows. Tools like vulnerability scanners and public exploit databases assist in this reconnaissance.
2. Crafting and injecting payloads: Once a vulnerability is identified, attackers craft malicious payloads tailored to the target environment. These payloads may be embedded in form fields, API requests, or file uploads, depending on the vulnerability and application architecture.
3. Exploitation: The malicious payload is delivered and executed by the target application or system. This can occur due to vulnerable components, inadequate input validation, logic flaws, or insecure runtime behaviors.
4. Code execution: Post-exploitation, attackers execute commands to achieve their objectives, such as creating backdoors, exfiltrating data, or deploying additional malware. Advanced attacks may use privilege escalation to gain deeper access to the system.
5. Persistence and propagation: To maintain access, attackers may install persistent mechanisms like rootkits or move laterally within the network to compromise other systems. This phase often involves disguising activity to avoid detection.

Related content: Read our guide to code execution vulnerability

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Common Vulnerabilities Leading to RCE 

Code Injection Attacks

Code injection attacks are a primary vector for RCE. These occur when an attacker inputs malicious code into a system via vulnerable application interfaces, such as form fields or URLs. The application then inadvertently executes this code as part of its normal processes. Code injection can enable unauthorized actions like data manipulation and system compromise. 

Attackers leverage code injection because they exploit insufficient validation and parsing practices within software applications. The flexibility and scripting capabilities in many programming environments make them susceptible to injection flaws. Common targets include SQL databases with SQL injection and web servers vulnerable to script injections. 

Deserialization Vulnerabilities

Deserialization vulnerabilities can lead to RCE when untrusted data is converted into objects in programming languages like Java or PHP without proper checks. Attackers craft serialized objects containing malicious payloads, which, when deserialized, can trigger unintended code execution pathways. 

Such attacks exploit the logic of serialization and deserialization processes, breaching application security boundaries and enabling malicious actions. Mitigating deserialization vulnerabilities requires a critical assessment of serialization logic and the application of strict input validation measures. 

Buffer Overflows

Buffer overflows occur when excess data overwrites memory buffers, potentially altering memory adjacent to the buffer space. This overflow can lead to arbitrary code execution if attackers inject payloads that manipulate program execution flow. Software written in languages like C and C++ is particularly susceptible due to manual memory management.

Mitigation techniques involve using programming practices that incorporate bounds checking and employing automated tools to detect potential overflow risks. Modern compilers provide options to add buffer security measures, and developers are encouraged to use safe libraries that abstract low-level buffer management. 

Out-of-Bounds Write Errors

Out-of-bounds write errors occur when a program writes data outside the boundaries of pre-allocated memory. This can unintentionally overwrite or corrupt critical memory regions, potentially leading to RCE if attackers manipulate memory contents to alter execution flows. Such errors often arise in programming languages that emphasize performance over safety.

Preventative strategies against out-of-bounds write errors include employing language features and compiler tools that enable bounds checking, as well as rigorous testing methodologies like fuzzing to identify points of failure. 

Recent Examples of Real-Life RCE Vulnerabilities 

RCE vulnerabilities allow attackers to execute arbitrary code on a target system, often leading to full system compromise. Below are recent examples of such vulnerabilities:

• CVE-2024-6386 in WPML Plugin for WordPress: Reported in December 2024, this vulnerability in the WPML plugin allows authenticated users to execute arbitrary code on the server, potentially leading to full site compromise.
• CVE-2024-45489 in Arc Browser: In September 2024, a vulnerability in the Arc browser's Boosts feature was revealed, allowing attackers to execute arbitrary code in other users' browser sessions by manipulating Boosts. The issue was promptly patched upon discovery.
• CVE-2024-38063 in Windows IPv6: Disclosed in August 2024, this critical RCE vulnerability affects all Windows operating systems utilizing IPv6. It has a CVSS score of 9.8, indicating its severity.
• Vulnerabilities in OpenVPN: In August 2024, multiple vulnerabilities were discovered in OpenVPN, including CVE-2024-27903, which allows remote code execution on Windows platforms. These vulnerabilities can be exploited by unauthenticated attackers, leading to system compromise.
• RegreSSHion (CVE-2024-6387) in OpenSSH: Reported in July 2024, this vulnerability in OpenSSH's server component allows remote code execution due to a signal handler race condition. It affects OpenSSH versions from 8.5p1 to 9.7p1 on glibc-based Linux systems.
• CVE-2024-3094 in XZ Utils: Discovered in March 2024, this backdoor in versions 5.6.0 and 5.6.1 of the XZ Utils compression software allowed attackers with a specific private key to execute arbitrary code on affected Linux systems.
• CVE-2024-0031 in Android System Component: In February 2024, Google patched a critical RCE vulnerability in the Android System component. This flaw affected Android versions 11 through 14 and could be exploited to execute arbitrary code on affected devices.

Mitigating and Preventing RCE Attacks 

Here are some of the main ways to prevent and minimize the impact of remote code execution attacks.

1. Input Validation and Sanitization

Unvalidated input remains a significant vector for exploiting vulnerabilities leading to RCE. By implementing strict validation rules and using sanitization functions, developers can filter out potentially harmful data, reducing the risk of successful exploits.

Validation should include both client-side and server-side checks to ensure comprehensive protection. Input should be validated for expected formats and constraints, and sanitized to escape special characters that could introduce vulnerabilities. Some frameworks and libraries offer built-in validation while sanitization can optimize efforts.

2. Regular Patching and Updates

Regular patching and updates are critical for maintaining security against RCE vulnerabilities. New vulnerabilities are constantly discovered and addressed by developers through patches. Failing to apply these updates timely leaves systems exposed to known attack vectors that could be leveraged for RCE. 

Maintaining an updated software inventory and routinely applying security patches is essential. Automated update systems can improve the efficiency of patch management, ensuring that security updates are applied promptly without manual intervention. 

3. Implementing the Principle of Least Privilege

The principle of least privilege minimizes the potential impact of RCE attacks by ensuring users and processes operate with the minimum levels of access necessary. This principle limits the pathways through which malicious code can execute once inside a system. By carefully configuring permissions, organizations can prevent malicious actors from exploiting elevated privileges to perform unauthorized actions.

Regular audits of user permissions and system configurations are crucial for sustaining this security measure. Automating the management of privileges with role-based access control (RBAC) tools simplifies the process, ensuring that only necessary permissions are granted and modified as per role requirements. This reduces the system's attack surface and helps contain breaches.

4. Using Web Application Firewalls

Web application firewalls (WAFs) offer an additional layer of protection against RCE attacks by filtering and monitoring HTTP traffic between the web application and the Internet. These firewalls help detect and block malicious requests that could lead to RCE. Configuring a WAF involves setting rules that identify and thwart suspicious patterns indicative of an attack.

Deploying WAFs can be advantageous in securing web applications against a variety of threats, including RCE, without requiring substantial changes to existing codebases. Keeping WAF rulesets updated and adapting them based on evolving threat intelligence ensures strong protection. 

5. Security Training for Developers

Understanding the mechanics and implications of RCE empowers developers to write secure code and recognize potential vulnerabilities in the development lifecycle. Training programs should cover secure coding practices, vulnerability scanning, and the latest security trends and threats.

By embedding a security-first mindset in development teams, organizations foster a culture of vigilance where developers actively seek to identify and mitigate vulnerabilities. This proactive approach helps in early detection and remediation of potential RCE paths, translating into more secure software products. 

6. Containerization and Sandboxing

By running applications within isolated environments, the risk of an RCE exploit affecting the broader system is contained. Containers and sandboxes limit the level of access code has to the host system, reducing the potential damage from malicious activities.

Adopting containerization tools like Docker and applying virtualization techniques adds layers of security, enabling controlled environments for application execution. Developers should ensure containers and sandboxes are configured with strict security measures to prevent escape attempts. 

7. Threat Modeling and Penetration Testing

Threat modeling involves analyzing systems to identify possible security weaknesses, while penetration testing simulates attacks to assess the effectiveness of security measures. Together, these practices provide insights into potential entry points and consequence scenarios.

By performing regular threat modeling and penetration testing, organizations can ensure that security measures are effective against RCE vulnerabilities. This helps uncover hidden weaknesses and enables tweaking of defensive strategies. 

8. Utilizing Cloud Application Detection and Response (CADR)

Cloud Application Detection and Response (CADR) solutions aid in identifying and mitigating RCE attacks in real time. CADR tools monitor application behavior, detect anomalies indicative of exploitation attempts, and respond to threats automatically or through guided actions. 

These solutions integrate monitoring, analytics, and remediation to address security incidents at the application level. CADR systems leverage techniques such as behavior analysis, signature-based detection, and machine learning to identify suspicious activities, such as unexpected code execution or unauthorized access attempts. 

Preventing RCE with Oligo Security

The rate of new vulnerabilities and exploitation has led to a rise in remote code execution attacks. Relying solely on vulnerability detection and remediation is no longer a sustainable approach for security teams of any size.

Oligo CADR profiles code behavior to detect the first signs of code injection exploits and subsequent remote code execution. See how Oligo prevents remote code execution today.