Varnish Cache

Varnish Cache at a glance

Varnish is a widely used open-source HTTP caching reverse proxy (a web accelerator), sitting in front of web servers to speed up delivery. Varnish ships regular releases plus security fixes; as a component in the request path handling untrusted traffic, timely patching matters.

For admins Varnish updates are usually low-risk (swap the package, reload), but its configuration language (VCL) can change between major versions — read the upgrade notes and test the VCL before upgrading. Because Varnish parses HTTP and caches responses, a flaw can have request-smuggling or cache-poisoning implications — apply security releases promptly. Keep the admin/management interface off the open network. Mind what gets cached (avoid caching sensitive, per-user content) and how TLS is terminated (often by a separate layer in front). After updating, verify that caching and the VCL behave correctly. Track the version and its support window; patchletter surfaces new Varnish releases.