Varnish Cache Resilience & CVE Suite

Simulates workspace memory allocation boundaries, HTTP/2 transport upgrade buffer splitting, HeaderPlus workspace overflows, and broken flow-control window thread starvation against Varnish Cache instances.

Target Varnish Cache / Enterprise Layer L7 Techniques 4 simulations Access Self-service / Quote

Suite Overview

Varnish Cache uses dedicated per-thread and per-session workspaces (workspace_client, workspace_backend). When unexpected pipelining or header expansion exceeds the fixed workspace boundary without proper error handling, worker threads can trigger assertions or panic restarts.

HTTP/1 Linger Pipelining Workspace Overflow (CVE-2026-40396)

cve_2026_40396 — Sends pipelined HTTP/1 requests interleaved with linger delays to test Varnish workspace boundary and assertion safety.

HTTP/2 Upgrade Speculative Workspace Exhaustion (CVE-2026-40394)

cve_2026_40394 — Sends Upgrade: h2c with trailing pipelined HTTP/2 preface payload to test Varnish transport upgrade buffer splitting safety.

Varnish Enterprise HeaderPlus Workspace Overflow (CVE-2026-40395)

cve_2026_40395 — Sends requests with high-cardinality header arrays to test Varnish vmod_headerplus / req0 workspace bounds.

Varnish HTTP/2 Broke Window Flow-Control Starvation (CVE-2024-30156)

cve_2024_30156 — Opens concurrent HTTP/2 streams with minimal flow-control window increments to evaluate Varnish worker thread release under credit exhaustion.

Safe Execution

All simulations run against your verified domain with real-time health checks and automatic circuit-breaker abortion.

Test your Varnish Cache tuning and resilience safely.

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