keel serves files only from the configured document root. Paths are normalized and opened relative to that directory. A request that would leave the root is rejected, including .., encoded dot segments, encoded slashes, and a symlink whose target is outside the root. A NUL in a percent-encoded path is rejected.

Each connection has a fixed header buffer, a header timeout, an idle timeout, a write timeout, and a cap on requests. When a worker's connection table is full, further connections are refused. Directory listings are off unless directory_listing is turned on. Request bodies are not read.

keel does not terminate TLS, authenticate clients, or isolate sites from each other beyond the single document root and the optional server_name check. Do not expose it directly on an untrusted network. Terminate TLS on a reverse proxy.

Please report a vulnerability to the maintainer privately, out of band, before opening a public issue. Non-sensitive defects can be filed as a normal bug report.