CVE-2021-42383 is a high-severity use-after-free vulnerability (CWE-416) found in the BusyBox utility, specifically within its awk applet. BusyBox is a widely used software suite that provides several Unix utilities in a single executable, commonly deployed in embedded systems, routers, IoT devices, and lightweight Linux distributions. The vulnerability arises in the 'evaluate' function of the awk applet when processing a crafted awk pattern. A use-after-free condition occurs when the program continues to use memory after it has been freed, which can lead to undefined behavior including crashes or arbitrary code execution. In this case, the flaw can be triggered remotely without user interaction, as indicated by the CVSS vector (AV:N/AC:L/PR:H/UI:N), although it requires high privileges (PR:H) to exploit. Successful exploitation can result in denial of service (DoS) by crashing the application or potentially allow an attacker to execute arbitrary code with elevated privileges, compromising confidentiality, integrity, and availability of the affected system. The CVSS score of 7.2 reflects the high impact and relatively low attack complexity, but the requirement for privileged access limits the attack surface somewhat. No known public exploits have been reported in the wild to date, and no specific affected versions are detailed, suggesting the vulnerability may affect multiple BusyBox versions prior to patching. Given BusyBox’s prevalence in embedded and network devices, this vulnerability poses a significant risk to systems relying on its awk functionality for processing scripts or commands.

For European organizations, the impact of CVE-2021-42383 can be substantial, especially for sectors relying heavily on embedded Linux systems such as telecommunications, industrial control systems, smart infrastructure, and IoT deployments. Exploitation could lead to denial of service, disrupting critical services or network infrastructure, or enable attackers to gain code execution with elevated privileges, potentially leading to full system compromise. This could affect confidentiality of sensitive data, integrity of system operations, and availability of services. Given that BusyBox is often embedded in routers, gateways, and network appliances, exploitation could facilitate lateral movement within networks or persistent footholds. Organizations in critical infrastructure, manufacturing, and telecommunications sectors in Europe could face operational disruptions and increased risk of espionage or sabotage. The lack of known exploits reduces immediate risk, but the high severity and potential for privilege escalation necessitate prompt attention.

1. Immediate patching or upgrading BusyBox to a version where this vulnerability is fixed is the most effective mitigation. Since no patch links are provided, organizations should monitor BusyBox official repositories and security advisories for updates. 2. Restrict access to systems running BusyBox awk applet to trusted administrators only, minimizing exposure to high-privilege accounts. 3. Implement strict network segmentation and firewall rules to limit access to embedded devices and network appliances that use BusyBox. 4. Employ application whitelisting and integrity monitoring on critical systems to detect unauthorized changes or execution of malicious scripts. 5. Conduct thorough audits of embedded devices and IoT endpoints to identify BusyBox usage and verify versions. 6. Where possible, disable or restrict awk applet usage in BusyBox if not required for operational purposes, reducing the attack surface. 7. Monitor logs and system behavior for signs of exploitation attempts, such as unexpected crashes or anomalous awk script executions. 8. Incorporate this vulnerability into vulnerability management and incident response plans to ensure rapid detection and remediation.