CVE-2025-23085 is a vulnerability identified in Node.js HTTP/2 server implementations affecting versions 18.x, 20.x, 22.x, and 23.x. The issue arises from improper handling of abrupt socket closures by remote peers that do not send a GOAWAY notification, as well as from connection terminations triggered by invalid HTTP/2 headers detected by the nghttp2 library. These conditions cause a memory leak (classified under CWE-401: Improper Release of Memory), leading to increased memory consumption on the server. Over time, this can exhaust system resources, resulting in denial of service (DoS) conditions. The vulnerability is exploitable remotely without requiring authentication or user interaction, making it accessible to unauthenticated attackers. The CVSS v3.0 score is 5.3 (medium severity), reflecting the impact limited to availability without compromising confidentiality or integrity. No patches were listed at the time of disclosure, and no known exploits have been reported in the wild. The flaw specifically impacts HTTP/2 server users on Node.js, which is widely used for scalable web applications and services. The vulnerability's root cause lies in the HTTP/2 protocol handling within Node.js's integration with the nghttp2 library, which manages HTTP/2 framing and connection lifecycle. Abrupt connection closures or malformed headers cause internal resources to remain allocated, leading to memory leaks.

For European organizations, this vulnerability poses a risk primarily to availability. Web services and APIs built on Node.js HTTP/2 servers may experience degraded performance or outages due to memory exhaustion if targeted by attackers exploiting this flaw. Organizations with high-volume or public-facing Node.js applications are particularly vulnerable to denial of service attacks that could disrupt business operations, customer access, and critical services. While the vulnerability does not expose sensitive data or allow unauthorized code execution, the resulting service disruption can have significant operational and reputational impacts. Sectors such as finance, e-commerce, government, and telecommunications, which rely heavily on Node.js for backend services, may face increased risk. Additionally, the lack of authentication or user interaction requirements lowers the barrier for exploitation, increasing the likelihood of opportunistic attacks. The absence of known exploits currently reduces immediate threat but does not eliminate future risk, especially as attackers often develop exploits post-disclosure.

European organizations should implement the following specific mitigations: 1) Monitor memory usage and connection metrics on Node.js HTTP/2 servers to detect abnormal resource consumption early. 2) Apply any official patches or updates from the Node.js project promptly once released. 3) Implement connection rate limiting and timeouts to reduce the impact of abrupt socket closures and malformed headers. 4) Use reverse proxies or web application firewalls (WAFs) capable of filtering malformed HTTP/2 traffic to prevent triggering the vulnerability. 5) Conduct regular security testing and fuzzing of HTTP/2 endpoints to identify and remediate related issues proactively. 6) Consider temporarily disabling HTTP/2 support if feasible until patches are available, especially on critical systems. 7) Maintain an inventory of Node.js versions in use and prioritize upgrades to unaffected or patched versions. 8) Collaborate with incident response teams to prepare for potential denial of service scenarios related to this vulnerability.