CVE-2019-15605 is a vulnerability classified as HTTP Request Smuggling (CWE-444) affecting multiple versions of the Node.js runtime environment, specifically versions 4.0 through 13.0. HTTP Request Smuggling exploits discrepancies in the way front-end and back-end servers parse and interpret HTTP requests, particularly when handling the Transfer-Encoding header. In this case, Node.js improperly processes malformed Transfer-Encoding headers, allowing an attacker to craft specially designed HTTP requests that can be interpreted differently by intermediary proxies and the Node.js server. This discrepancy enables the attacker to smuggle malicious payloads through the HTTP request pipeline, potentially bypassing security controls, injecting unauthorized requests, or manipulating the request stream. The vulnerability arises because Node.js does not correctly validate or normalize the Transfer-Encoding header, which is critical in determining how the HTTP message body is framed. Although no known exploits have been reported in the wild, the vulnerability poses a significant risk due to the widespread use of Node.js in web applications and backend services. The lack of a CVSS score indicates that the vulnerability has not been fully assessed for severity, but the technical nature suggests a high risk if exploited. The vulnerability affects a broad range of Node.js versions, including long-term support (LTS) releases, increasing the potential attack surface. Since Node.js is often deployed in environments exposed to the internet and used to build APIs, web servers, and microservices, this vulnerability could be leveraged to conduct attacks such as request hijacking, session fixation, cache poisoning, or bypassing security filters.

For European organizations, the impact of CVE-2019-15605 can be substantial, especially for those relying heavily on Node.js for their web infrastructure, including e-commerce platforms, financial services, government portals, and critical infrastructure management systems. Exploitation could lead to unauthorized access, data leakage, or manipulation of HTTP requests, undermining confidentiality and integrity. Attackers could bypass security controls such as web application firewalls (WAFs) or intrusion detection systems (IDS) by smuggling malicious requests, potentially leading to further exploitation like credential theft or lateral movement within networks. The availability of services could also be affected if attackers use the vulnerability to inject malformed requests that cause server crashes or resource exhaustion. Given the prevalence of Node.js in modern web development, the scope of affected systems is broad, increasing the risk of widespread impact. The vulnerability does not require authentication, making it accessible to remote attackers, and does not depend on user interaction, which heightens the threat level. European organizations with public-facing Node.js applications are particularly at risk, and the potential for supply chain attacks exists if Node.js-based components are integrated into larger software ecosystems.

To mitigate this vulnerability, European organizations should prioritize upgrading Node.js to versions beyond 13.0 where the vulnerability is patched. Since no official patch links are provided in the data, organizations should monitor Node.js security advisories and apply updates promptly once available. In the interim, organizations can implement strict input validation and normalization of HTTP headers at the application or proxy level to detect and block malformed Transfer-Encoding headers. Deploying robust web application firewalls configured to identify HTTP request smuggling patterns can help mitigate exploitation attempts. Network segmentation and limiting exposure of Node.js services to trusted networks reduce the attack surface. Additionally, conducting thorough code reviews and penetration testing focused on HTTP request handling can identify vulnerable endpoints. Logging and monitoring HTTP traffic for anomalies related to Transfer-Encoding headers can provide early detection of exploitation attempts. Organizations should also educate developers about secure HTTP header handling and encourage the use of updated libraries and frameworks that address this vulnerability. Finally, implementing layered security controls, including rate limiting and anomaly detection, can further reduce risk.