CVE-2022-35256 is a medium-severity vulnerability affecting the Node.js HTTP module, specifically the llhttp parser component used in versions 4.0 through 18.0. The vulnerability arises because the parser does not correctly handle HTTP header fields that are not terminated with the standard CRLF (Carriage Return Line Feed) sequence. This improper handling can lead to HTTP Request Smuggling (CWE-444), a technique where an attacker crafts specially malformed HTTP requests to bypass security controls, poison web caches, or interfere with the processing of legitimate requests. HTTP Request Smuggling exploits discrepancies in how front-end proxies, load balancers, and backend servers parse HTTP requests, potentially allowing attackers to inject malicious requests or manipulate session data. In this case, the vulnerability is due to the llhttp parser's failure to strictly enforce header termination rules, enabling attackers to smuggle requests through Node.js-based HTTP servers or applications. The CVSS v3.1 base score is 6.5, indicating a medium severity, with an attack vector of network (AV:N), low attack complexity (AC:L), no privileges required (PR:N), no user interaction (UI:N), and impacts on confidentiality and integrity but not availability. No known exploits in the wild have been reported as of the publication date, but the vulnerability is publicly disclosed and can be targeted in unpatched systems. Since Node.js is widely used in web applications and services, this vulnerability can affect a broad range of deployments, especially those exposing HTTP endpoints directly or behind proxies that do not normalize or validate HTTP headers properly. The absence of a patch link suggests that remediation may require upgrading Node.js to a version where the llhttp parser is fixed or applying vendor-provided patches once available.

For European organizations, the impact of CVE-2022-35256 can be significant, particularly for those relying on Node.js for web services, APIs, or microservices architectures. Successful exploitation could allow attackers to bypass security controls such as web application firewalls or reverse proxies, leading to unauthorized access to sensitive information (confidentiality impact) or manipulation of data (integrity impact). This could result in data breaches, session hijacking, or injection of malicious payloads that compromise application logic. Although availability is not directly impacted, the indirect consequences of compromised integrity or confidentiality could disrupt business operations, damage reputation, and lead to regulatory non-compliance under GDPR or other data protection laws. Organizations in sectors with high reliance on web applications—such as finance, healthcare, e-commerce, and government—are particularly at risk. The vulnerability's network-based attack vector and lack of required privileges or user interaction make it relatively easy to exploit remotely, increasing the threat surface. Given the widespread use of Node.js in Europe, especially in startups, SMEs, and large enterprises adopting JavaScript-based backend technologies, the potential for exploitation exists wherever vulnerable versions are deployed without adequate mitigations.

To mitigate CVE-2022-35256 effectively, European organizations should: 1) Immediately inventory all Node.js deployments to identify versions between 4.0 and 18.0 in use, prioritizing internet-facing services. 2) Upgrade Node.js to the latest stable release where the llhttp parser vulnerability is addressed; if an official patch is not yet available, monitor vendor advisories closely and apply patches promptly once released. 3) Implement strict input validation and normalization at the HTTP proxy or load balancer level to reject or sanitize malformed headers that do not conform to HTTP standards, preventing smuggled requests from reaching backend Node.js servers. 4) Employ Web Application Firewalls (WAFs) with rules specifically designed to detect and block HTTP Request Smuggling attempts, including anomalies in header termination sequences. 5) Conduct thorough security testing, including fuzzing and penetration testing focused on HTTP request parsing, to detect potential smuggling vulnerabilities in custom or third-party middleware. 6) Monitor network traffic and application logs for unusual patterns indicative of request smuggling, such as unexpected request boundaries or header anomalies. 7) Educate development and operations teams about the risks of HTTP Request Smuggling and best practices for secure HTTP header handling. These measures, combined with timely patching, will reduce the risk of exploitation and protect the confidentiality and integrity of web applications.