CVE-2026-49835: Sigstore Timestamp Authority has OOM due to unbounded metric label cardinality

An unauthenticated remote attacker can trigger unbounded memory growth on the timestamp authority server.

This vulnerability exists because the global wrapMetrics middleware records the raw HTTP request path (r.URL.Path) and raw HTTP request method (r.Method) as Prometheus labels for latency and request count metric vectors. Since this middleware runs before standard routing occurs, it executes for all incoming requests, including those for unmatched paths (yielding 404 responses) or arbitrary request methods. The Prometheus library registers a new, permanent time-series entry for every distinct label combination. An attacker can continuously issue requests containing random paths (e.g., /api/v1/timestamp/<uuid>) or random HTTP methods to exhaust system memory.