Command injection

With a command injection attack, an attacker can hijack a vulnerable application in order to execute arbitrary commands on the host operating system. Command injection is made possible when an application doesn’t check user input carefully and passes unsafe user-supplied data (forms, cookies, HTTP headers, etc.) to a system shell. In this attack, the attacker-supplied operating system commands are usually executed with the privileges of the vulnerable application.

What are command injection vulnerabilities?

Command injection vulnerabilities are most often found in older, legacy code, such as CGI scripts. By identifying a critical vulnerability, attackers can insert malicious code in an application, gaining functionality and ultimately executing specific commands that infect the targeted user and system networks. Under this command injection attack, functionality on the application server can be modified and invoked. With unauthorized access to data, an account can add additional commands and potentially take complete control of the web server’s host operating system.

Command injection methods

Command injection allows attackers to execute arbitrary system commands on a device, often leading to complete compromise of the targeted system. Command injection occurs when an application fails to properly check user input before passing it to operating system commands. This flaw allows attackers to inject malicious commands that are executed with the privileges of the vulnerable application. 

Command injection exploits stem from trusting user input and using it unsafely in system-level operations. This vulnerability often arises in applications that interact with system utilities, especially when developers use insecure methods like concatenation to build commands.

Command injection is less common than other injection vulnerabilities because modern development frameworks and practices discourage direct interaction with the operating system. High-level libraries often provide safer abstractions, making it unnecessary to invoke shell commands directly. Additionally, secure coding guidelines and security-focused frameworks help reduce the frequency of these vulnerabilities.

Code injection vs. command injection

Code injection and command injection are both serious security vulnerabilities, but they differ in their targets and impacts. Code injection involves inserting malicious code into a vulnerable application to manipulate its behavior or gain unauthorized access. This code runs within the application’s runtime environment, such as its programming language interpreter or framework. For example, attackers might exploit vulnerabilities to inject SQL queries, JavaScript or other types of executable code. A common scenario is SQL injection, where malicious input alters a database query to reveal sensitive data or bypass authentication. The scope of code injection is usually confined to the application’s execution environment, making it primarily a risk to the integrity and functionality of the application itself.

In contrast, command injection targets the operating system, allowing attackers to execute arbitrary system-level commands through a vulnerable application. This vulnerability typically arises when user input is passed to system calls without proper validation or sanitization. For instance, an application using shell commands to process input may inadvertently allow an attacker to chain additional commands, enabling actions like file deletion, privilege escalation or unauthorized access to the server. Because command injection affects the underlying operating system, its consequences are often more severe and can result in complete system compromise.

The key difference between these two vulnerabilities lies in their scope and level of control. Code injection exploits the application’s internal logic or language interpreter, while command injection exploits its interaction with the operating system. To mitigate these threats, developers must validate and sanitize all user inputs, avoid insecure coding practices and use safer alternatives such as prepared statements for database queries or language-specific libraries for system interactions.

Command injection vulnerability examples

Command injection vulnerabilities continue to be identified in a wide variety of systems, leading to significant security breaches. For instance, in July 2024, the Cybersecurity and Infrastructure Security Agency (CISA) issued a security alert highlighting the dangers of command injection vulnerabilities. The article called out multiple exploited command injection flaws in network edge devices, including:

• CVE-2024-20399 — Cisco NX-OS Software CLI Command Injection Vulnerability
• CVE-2024-3400 — PAN-OS: Arbitrary File Creation Leads to OS Command Injection Vulnerability in GlobalProtect
• CVE-2024-21887 — Ivanti Connect Secure (9.x, 22.x) and Ivanti Policy Secure (9.x, 22.x) Command injection vulnerability in web components

One notable example of a command injection vulnerability being exploited in the wild is CVE-2024-51378, a vulnerability that affects the WordPress management platform CyberPanel. The vulnerability was discovered by security researchers and disclosed in October 2024. Initial reports showed more than 22,000 instances of CyberPanel — which were managing a total of more than 152,000 domains — that were publicly accessible and exposed to the critical command injection vulnerability.. In less than 24 hours, the majority of these systems were mass-targeted by threat actors, resulting in the deployment of PSAUX ransomware alongside cryptominer software and other ransomware variants.

These examples highlight the devastating potential of command injection vulnerabilities, especially when attackers can exploit them at scale. The rapid targeting of vulnerable systems demonstrates how quickly unpatched command injection flaws can lead to widespread compromises, emphasizing the need for immediate remediation and proactive security measures.

Command injection consequences

When command injection vulnerabilities are discovered, the impact can be catastrophic. Successful exploitation often gives attackers direct access to the system, enabling them to execute arbitrary commands, steal sensitive data, delete critical files or move laterally within a network. The payoff for attackers lies in the complete control they can achieve, often with minimal effort. This combination of rarity and high impact makes command injection a prized vulnerability for attackers.

Command injection prevention

Mitigating command injection begins with secure coding practices. Developers should avoid using system commands whenever safer alternatives exist. For instance, rather than invoking a shell command to manipulate files, a developer could use native language libraries that offer equivalent functionality without the risks of command injection.

Input validation is also essential. Applications should validate all user input against a strict set of criteria, rejecting any data that doesn’t conform to expected formats. This approach ensures that only safe, predictable inputs are processed.

Regular security audits and code reviews are crucial, particularly for legacy applications or those interacting with sensitive systems. Automated scanning tools can help identify vulnerabilities before attackers do.

Can endpoint detection and response (EDR) tools prevent command injection attacks?

While EDR tools are decent at catching some of the more basic command injection attacks, they fail to detect and prevent a command injection attack under certain circumstances, especially when the attack is highly obfuscated or uses methods that evade typical detection mechanisms. 

Consider this scenario of a blind command injection in a trusted application:

1. A web application running on a corporate network allows users to upload files and specify commands for processing (e.g., renaming a file or resizing an image). This application is trusted and has administrative privileges on the server.
2. The application fails to properly sanitize user inputs in the command-line arguments it passes to a shell command (e.g., system() or exec()).
3. An attacker uploads a specially crafted payload, such as a filename like file.txt; rm -rf /important-data.The application concatenates this input into a shell command: mv uploaded_files/file.txt; rm -rf /important-data uploaded_files/processed_file.txt The injected command rm -rf /important-data executes on the server.

Why would EDR not be effective in this instance? For one, the command is executed by a legitimate and trusted application, not a malicious executable. Further, the attacker encodes or splits the payload into smaller, less suspicious-looking parts that are assembled at runtime.

Plus, EDR might not recognize the deletion of /important-data as unusual for this application, especially if similar operations are part of its regular workflow. If the EDR isn’t configured to monitor file system changes in real time, it may not detect the deletion until it’s too late.

In the above scenario, when the EDR tool invariably would neither  detect nor prevent the attack, the attacker successfully executes the command, thereby compromising or damaging the system. The EDR tool fails to detect the attack due to the lack of anomaly detection or visibility into command arguments processed by legitimate applications.

How can an attack like this be mitigated? Advanced behavioral analytics that flag unusual activities — even from trusted applications — would help, as would the real-time monitoring of critical file paths and configuration. In many instances, only a tool with deep application context — such as Contrast Application Detection and Response (ADR) — can successfully identify and prevent these attacks.

The importance of Contrast ADR in Command Injection Prevention

ADR is a critical capability that addresses the application-layer visibility gap in threat detection and response. Current security monitoring tools that provide visibility into cloud, network and endpoint activity miss the intricate details of what is attacking the application layer. This is where ADR plays a critical role, providing granular visibility into what lines of code are being exploited, along with data flow and application logic and API behavior, recognizing and identifying anomalies and enabling precise threat detection and response across the entire application layer. 

Contrast ADR is a critical security measure for identifying and mitigating exploits including command injection, reflected XSS and path traversal at runtime. Taking an “inside-out” approach, Contrast ADR detects applications attacks in flight — i.e., attackers exploiting live vulnerabilities in the application, be they in custom or open-source (OSS) code — as the attacks are occuring. Contrast ADR transmits threat and attack data to the SOC tooling for incident response workflows, including sending an alert to a SIEM and/or SOAR solution. It also enriches alerts with data about the state of the attack and the relevant vulnerabilities being exploited. Contrast ADR intel becomes part of your SOAR playbooks that drive incident response workflows.

Proactively deploying Contrast ADR to protect all your critical applications reduces the window of attack exposure and prevents command injection exploits from escalating into full-scale breaches, safeguarding critical applications and sensitive data.

Command injection vulnerabilities may be rare, but their impact is disproportionately severe. When exploited, they provide attackers with a powerful foothold in a system, often enabling complete compromise. Organizations must prioritize proactive measures to prevent, detect and respond to these dangerous exposures.