CVE-2021-44533 is a vulnerability in Node.js versions prior to 12.22.9, 14.18.3, 16.13.2, and 17.3.1 that relates to improper certificate validation, specifically involving the handling of multi-value Relative Distinguished Names (RDNs) in X.509 certificates. The issue arises because Node.js incorrectly interprets certificate subjects containing a single-value RDN as if they were multi-value RDNs. This ambiguity allows an attacker to craft a malicious certificate subject that injects an additional Common Name (CN) attribute. Such injection can bypass certificate subject verification processes that rely on Node.js's parsing behavior, potentially allowing attackers to impersonate legitimate entities or intercept communications that depend on certificate validation for authentication and trust. Notably, Node.js versions that do not accept multi-value RDNs are not vulnerable themselves; however, third-party applications or libraries that use Node.js's ambiguous certificate subject representation may be susceptible to exploitation. This vulnerability falls under CWE-295, which concerns improper certificate validation, a critical aspect of secure TLS/SSL communications. There are no known exploits in the wild, and no CVSS score has been assigned. The vulnerability was publicly disclosed in February 2022, with affected versions spanning a wide range of Node.js releases from 4.0 through 17.0, indicating a long-standing issue in the Node.js ecosystem. The lack of patch links suggests that users should upgrade to the fixed versions (12.22.9, 14.18.3, 16.13.2, 17.3.1 or later) to mitigate this risk.

For European organizations, this vulnerability poses a significant risk to the confidentiality and integrity of communications that rely on Node.js-based applications performing certificate validation. Since Node.js is widely used in web servers, APIs, and microservices, improper certificate validation could allow attackers to perform man-in-the-middle (MITM) attacks by presenting malicious certificates that bypass subject verification. This could lead to unauthorized data access, credential theft, or injection of malicious content. The impact is particularly critical for sectors that rely heavily on secure communications, such as finance, healthcare, government, and critical infrastructure. Additionally, organizations using third-party Node.js libraries or frameworks that do not handle multi-value RDNs correctly may inadvertently expose themselves to this vulnerability even if their Node.js runtime is patched. The absence of known exploits in the wild reduces immediate risk but does not eliminate the potential for targeted attacks, especially in high-value environments. The vulnerability does not directly affect availability but can undermine trust in secure communications, potentially leading to broader security incidents and compliance violations under regulations like GDPR.

1. Upgrade Node.js to the fixed versions: 12.22.9, 14.18.3, 16.13.2, 17.3.1 or later. This is the most effective mitigation to ensure the core runtime correctly handles multi-value RDNs. 2. Audit and update all third-party Node.js libraries and frameworks that perform certificate validation to ensure they correctly handle multi-value RDNs and do not rely solely on Node.js's certificate subject parsing. 3. Implement additional certificate validation layers where possible, such as using well-maintained TLS libraries or external validation services that are known to correctly parse and validate certificate subjects. 4. Employ strict certificate pinning and validation policies in applications to reduce reliance on potentially ambiguous certificate parsing. 5. Monitor network traffic for unusual TLS handshake anomalies or unexpected certificate subjects that could indicate exploitation attempts. 6. Educate development and security teams about the risks of improper certificate validation and encourage secure coding practices around TLS and certificate handling. 7. Conduct penetration testing and code reviews focused on certificate validation logic in Node.js applications to identify and remediate potential vulnerabilities.