The vulnerability CVE-2026-21440 in the @adonisjs/bodyparser npm package is a critical path traversal flaw with a CVSS score of 9.2, affecting the multipart file handling mechanism of the AdonisJS framework. The issue stems from the MultipartFile.move(location, options) function, where if the 'options' argument is omitted or the filename is not explicitly sanitized, the system defaults to using the client-supplied filename without validation. This allows an attacker to craft filenames containing directory traversal sequences (e.g., '../') to write files outside the intended upload directory. If the overwrite flag is set to true, attackers can overwrite existing files, including application code, configuration files, or startup scripts. This can lead to remote code execution (RCE) if the overwritten files are executed or loaded by the application or runtime environment. Exploitation requires a reachable file upload endpoint that uses the vulnerable bodyparser version. The flaw affects AdonisJS versions <=10.1.1 and <=11.0.0-next.5, with fixes released in 10.1.2 and 11.0.0-next.6 respectively. The vulnerability was responsibly disclosed by Hunter Wodzenski. The risk is heightened in deployments where filesystem permissions and application architecture allow overwriting critical files. This vulnerability is part of a broader trend of path traversal issues in npm packages, coinciding with a similar flaw in the jsPDF library. The AdonisJS framework is popular in Node.js environments for building web applications and APIs, making this vulnerability significant for developers and organizations relying on it. The flaw underscores the importance of sanitizing user input, especially filenames in file upload features, and applying strict controls on file system operations in web applications.

For European organizations, this vulnerability poses a significant risk to web servers and API endpoints built with AdonisJS that use the vulnerable bodyparser package. Successful exploitation can lead to arbitrary file writes, allowing attackers to overwrite critical files such as application code, configuration files, or startup scripts. This can result in remote code execution, data breaches, service disruption, and potential lateral movement within networks. Organizations with publicly accessible upload endpoints are particularly vulnerable. The impact extends to confidentiality, integrity, and availability of systems and data. Given the widespread use of Node.js and frameworks like AdonisJS in Europe’s tech ecosystem, especially in sectors like finance, healthcare, and government, the threat could disrupt critical services and lead to regulatory compliance issues under GDPR if personal data is compromised. Additionally, the ability to execute arbitrary code remotely increases the risk of ransomware deployment or persistent backdoors. The lack of known exploits in the wild currently provides a window for proactive mitigation, but the critical severity demands immediate attention.

1. Immediately update the @adonisjs/bodyparser package to version 10.1.2 or later (or 11.0.0-next.6 for next releases) to apply the official patch. 2. Audit all AdonisJS applications to identify and secure any file upload endpoints, ensuring they do not rely on unsanitized filenames. 3. Implement strict filename sanitization and validation routines to reject or safely handle any path traversal sequences in uploaded filenames. 4. Configure the MultipartFile.move() function to always use the 'options' argument with sanitized filenames and avoid defaulting to client-supplied names. 5. Restrict file system permissions for the application process to the minimum necessary, preventing overwriting of critical files or directories. 6. Employ runtime application self-protection (RASP) or web application firewalls (WAF) with rules to detect and block path traversal attempts. 7. Monitor logs for suspicious file upload activity or unexpected file modifications. 8. Conduct penetration testing focusing on file upload functionalities to verify the absence of path traversal vulnerabilities. 9. Educate developers on secure file handling practices and the risks of unsanitized user input. 10. Consider isolating upload directories and using containerization or sandboxing to limit the impact of potential exploits.