CVE-2026-27630 identifies a critical Denial of Service vulnerability in TinyWeb, a lightweight web server written in Delphi for Win32 platforms. Versions prior to 2.02 are vulnerable to a Slowloris attack, a technique where an attacker opens numerous connections to the server and sends data extremely slowly (for example, one byte every few minutes). TinyWeb’s architecture spawns a new operating system thread for each incoming connection but lacks mechanisms to limit the maximum number of concurrent connections or to enforce request timeouts. This design flaw allows an unauthenticated remote attacker to exhaust server resources such as memory and thread handles by maintaining many slow, incomplete connections. The consequence is a denial of service, rendering the server unresponsive to legitimate requests. The vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption). The vendor fixed the issue in version 2.02 by introducing a maximum connection limit (CMaxConnections set to 512) and an idle connection timeout (CConnectionTimeoutSecs set to 30 seconds). These controls prevent resource exhaustion by limiting concurrency and terminating idle connections. No known exploits are currently reported in the wild, but the vulnerability’s characteristics make exploitation straightforward. As a temporary mitigation, deploying TinyWeb behind a reverse proxy or Web Application Firewall (WAF) such as nginx, HAProxy, or Cloudflare is recommended. These intermediaries can buffer incomplete requests, enforce connection limits, and apply aggressive timeouts to mitigate slow HTTP attacks. This vulnerability affects any organization using TinyWeb versions before 2.02, especially those exposing the server directly to the internet without protective layers.

The primary impact of CVE-2026-27630 is a Denial of Service condition that can severely disrupt availability of web services hosted on vulnerable TinyWeb servers. By exhausting server threads and memory, attackers can cause the server to become unresponsive, leading to downtime and loss of service for legitimate users. This can affect business continuity, customer trust, and operational efficiency. Organizations relying on TinyWeb for critical web applications or services may face significant operational disruptions. The vulnerability requires no authentication or user interaction, increasing the risk of widespread exploitation. Although no exploits are currently known in the wild, the simplicity of the attack method and the lack of built-in protections in affected versions make it a high-risk vulnerability. Additionally, organizations without robust network defenses or traffic filtering are particularly vulnerable. The impact is largely on availability, with no direct confidentiality or integrity compromise reported. However, prolonged denial of service can indirectly affect organizational reputation and revenue.

To mitigate CVE-2026-27630, organizations should prioritize upgrading TinyWeb to version 2.02 or later, which includes built-in protections such as maximum connection limits and idle connection timeouts. If immediate upgrading is not feasible, deploy TinyWeb behind a robust reverse proxy or Web Application Firewall (WAF) like nginx, HAProxy, or Cloudflare. These intermediaries should be configured to buffer incomplete HTTP requests, enforce strict connection concurrency limits, and apply aggressive idle timeouts (e.g., 30 seconds or less). Network-level rate limiting and connection throttling can further reduce attack surface. Monitoring for unusual connection patterns, such as many slow or incomplete connections, can help detect ongoing attacks. Additionally, consider implementing TCP SYN cookies or other kernel-level protections to mitigate resource exhaustion. Regularly review server logs and network traffic for signs of Slowloris or similar slow HTTP attacks. Finally, incorporate this vulnerability into incident response plans to ensure rapid detection and mitigation if exploitation attempts occur.