CVE-2025-59465 is a vulnerability in the Node.js runtime environment that arises from improper handling of malformed HTTP/2 HEADERS frames containing oversized or invalid HPACK-encoded data. When such a frame is received, it triggers an unhandled error on the TLSSocket object, specifically an ECONNRESET error, which causes the Node.js process to crash instead of gracefully closing the connection. This behavior results in a remote denial of service (DoS) condition. The vulnerability affects a wide range of Node.js versions, from early releases (4.0) through recent versions (up to 25.2.1), indicating a long-standing issue or a regression. The root cause is the lack of explicit error handling on secure sockets; applications that do not attach error event listeners to the 'secureConnection' event are vulnerable. The attack vector is network-based, requiring no privileges or user interaction, making exploitation straightforward for remote attackers. While no known exploits have been reported in the wild, the vulnerability's characteristics suggest it could be weaponized to disrupt services relying on Node.js HTTP/2 servers. The CVSS v3.0 score of 7.5 reflects the high impact on availability with no confidentiality or integrity loss. The vulnerability is particularly relevant for web servers, APIs, and microservices implemented in Node.js that utilize HTTP/2 over TLS. The absence of patches at the time of publication necessitates immediate mitigation through application-level error handling and monitoring for official updates from the Node.js project.

For European organizations, this vulnerability poses a significant risk to the availability of Node.js-based services, including web applications, APIs, and backend microservices. A successful exploit can cause unexpected process crashes, leading to denial of service and potential disruption of business-critical operations. This can affect customer-facing portals, internal tools, and cloud services that depend on Node.js HTTP/2 servers. The broad range of affected Node.js versions means many legacy and current deployments are vulnerable. Service downtime can result in financial losses, reputational damage, and compliance issues, especially for sectors with strict uptime requirements such as finance, healthcare, and e-government. Additionally, the ease of exploitation without authentication increases the threat landscape, potentially enabling attackers to conduct DoS attacks at scale. European organizations with limited error handling practices on secure sockets are particularly exposed. The lack of known exploits in the wild currently reduces immediate risk but does not eliminate the threat, as attackers may develop exploits rapidly once the vulnerability is public.

1. Immediately review and update Node.js applications to attach explicit error handlers to all secure sockets, particularly listening for 'error' events on TLSSocket instances to prevent unhandled exceptions that crash the process. 2. Monitor Node.js official channels for patches addressing CVE-2025-59465 and apply updates promptly once available. 3. Implement robust process management and automatic restart mechanisms (e.g., using PM2, systemd, or container orchestration platforms) to minimize downtime in case of crashes. 4. Employ network-level protections such as rate limiting and filtering to detect and block malformed HTTP/2 traffic patterns that could trigger the vulnerability. 5. Conduct thorough testing of HTTP/2 handling in development and staging environments to ensure error resilience. 6. Audit existing Node.js versions in use across the organization to identify and prioritize upgrades or mitigations for vulnerable instances. 7. Educate development teams on secure socket error handling best practices to prevent similar issues. 8. Consider deploying Web Application Firewalls (WAFs) capable of inspecting HTTP/2 traffic to mitigate malformed frame attacks.