CVE-2025-9784

A flaw was found in Undertow where malformed client requests can trigger server-side stream resets without triggering abuse counters. This issue, referred to as the "MadeYouReset" attack, allows malicious clients to induce excessive server workload by repeatedly causing server-side stream aborts. While not a protocol bug, this highlights a common implementation weakness that can be exploited to cause a denial of service (DoS).

This vulnerability is rated with an Important severity. It is simple to exploit because it does not require authentication and could result in a Denial of Service (DoS). While some DoS flaws are classified as Moderate, “MadeYouReset” is Important because of the limited barriers (no specialized tooling or advanced scripting) to exploitation, which directly impacts service availability. The vulnerability arises from an implementation weakness in HTTP/2 stream reset handling — malformed client requests can trigger server-side resets without incrementing abuse counters, allowing an attacker to bypass built-in request throttling and overhead limits. Since these resets consume CPU and memory resources and can be generated at scale over a single TCP/TLS connection, a remote attacker could exhaust server capacity quickly, impacting all legitimate clients.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.