CVE-2024-27983 is a high-severity vulnerability affecting Node.js HTTP/2 server implementations across a wide range of versions from 4.0 through 21.0. The vulnerability arises due to a race condition in the handling of HTTP/2 CONTINUATION frames within the nghttp2 library used by Node.js. Specifically, when an attacker sends a small number of HTTP/2 frames, including CONTINUATION frames, and then abruptly closes the TCP connection, the Http2Session destructor is triggered while header frames are still being processed and stored in memory. This leads to residual data remaining in nghttp2 memory after a reset, causing a race condition (CWE-362). The consequence of this flaw is that an attacker can cause the Node.js HTTP/2 server to become completely unavailable, effectively resulting in a denial-of-service (DoS) condition. The vulnerability requires no authentication or user interaction and can be exploited remotely over the network. The CVSS v3.0 score is 8.2, reflecting a high severity with network attack vector, low attack complexity, no privileges required, no user interaction, unchanged scope, no confidentiality impact, limited integrity impact, and high availability impact. No known exploits are currently reported in the wild, and no patches are linked yet. This vulnerability is particularly critical for environments relying on Node.js HTTP/2 servers for web services, APIs, or microservices, as it can be triggered with minimal traffic to disrupt service availability.

For European organizations, the impact of CVE-2024-27983 can be significant, especially for those heavily utilizing Node.js for backend services exposed via HTTP/2. The vulnerability enables attackers to cause denial-of-service conditions remotely without authentication, potentially disrupting critical web applications, APIs, and real-time services. This can lead to service outages, loss of business continuity, and reputational damage. Sectors such as finance, e-commerce, telecommunications, and public services that rely on Node.js for scalable web infrastructure are particularly at risk. Additionally, the disruption of availability can indirectly affect data integrity and customer trust. Given the widespread adoption of Node.js in European IT ecosystems, the vulnerability could be exploited to target high-value organizations or critical infrastructure, especially if combined with other attack vectors. The lack of known exploits currently provides a window for proactive mitigation, but the ease of exploitation and network accessibility make timely remediation essential.

1. Immediate mitigation should focus on monitoring and limiting abnormal HTTP/2 traffic patterns, particularly unusual sequences of CONTINUATION frames followed by abrupt TCP connection closures. Implementing rate limiting and anomaly detection on HTTP/2 connections can reduce exposure. 2. Deploy Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) with custom rules to detect and block malformed or suspicious HTTP/2 frame sequences. 3. Where possible, temporarily disable HTTP/2 support on Node.js servers until patches are available, especially in high-risk environments. 4. Maintain strict network segmentation and apply access controls to limit exposure of Node.js HTTP/2 servers to untrusted networks. 5. Keep Node.js versions updated and monitor official Node.js and nghttp2 project channels for patches addressing this vulnerability. 6. Conduct thorough testing of Node.js HTTP/2 server implementations under simulated attack conditions to assess resilience and identify potential service degradation. 7. Educate development and operations teams about this vulnerability to ensure rapid response and patch deployment once available. These steps go beyond generic advice by focusing on HTTP/2 protocol-specific traffic analysis, temporary protocol disablement, and proactive network defense tailored to the vulnerability's exploitation method.