CVE-2026-27630: TinyWeb vulnerable to Remote Denial of Service via Thread/Connection Exhaustion (Slowloris)
TinyWeb is a web server (HTTP, HTTPS) written in Delphi for Win32. Versions prior to version 2.02 are vulnerable to a Denial of Service (DoS) attack known as Slowloris. The server spawns a new OS thread for every incoming connection without enforcing a maximum concurrency limit or an appropriate request timeout. An unauthenticated remote attacker can exhaust server concurrency limits and memory by opening numerous connections and sending data exceptionally slowly (e.g. 1 byte every few minutes). Anyone hosting services using TinyWeb is impacted. Version 2.02 fixes the issue. The patch introduces a CMaxConnections limit (set to 512) and a CConnectionTimeoutSecs idle timeout (set to 30 seconds). As a temporary workaround if upgrading is not immediately possible, consider placing the server behind a robust reverse proxy or Web Application Firewall (WAF) such as nginx, HAProxy, or Cloudflare, configured to buffer incomplete requests and aggressively enforce connection limits and timeouts.
Affected Software
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Frequently Asked Questions
What is the severity of CVE-2026-27630?
CVE-2026-27630 is classified as a high severity vulnerability due to its potential for causing a Remote Denial of Service via Thread/Connection Exhaustion.
How do I fix CVE-2026-27630?
To mitigate CVE-2026-27630, upgrade to TinyWeb version 2.02 or later, which resolves the vulnerability.
What type of attack is CVE-2026-27630 associated with?
CVE-2026-27630 is associated with a Denial of Service (DoS) attack known as Slowloris.
Which versions of TinyWeb are affected by CVE-2026-27630?
TinyWeb versions prior to 2.02 are affected by CVE-2026-27630.
What is the impact of CVE-2026-27630 on users?
The impact of CVE-2026-27630 on users can lead to server unavailability as the vulnerability allows attackers to exhaust server resources.