opentelemetry-java: Quadratic CPU consumption in W3C tracestate parsing

Summary

OpenTelemetry Java's W3C trace-context propagator permits excessive CPU consumption when extracting crafted tracestate headers, potentially leading to denial of service. Regex backtracking causes quadratic parsing time for headers containing long runs of spaces or tabs without a following comma.

Impact

An unauthenticated attacker whose headers reach W3CTraceContextPropagator.extract() can cause excessive CPU usage through crafted requests. Parsing blocks the calling thread, potentially affecting other connections when extraction runs on a shared event-loop thread. Actual impact depends on ingress header-size limits, proxy configuration, and threading. Header-size limits reduce the per-request cost but do not eliminate the vulnerability.

Patches

Upgrade io.opentelemetry:opentelemetry-api to version 1.67.0 or later. PR #8914 replaces regex delimiter splitting with literal comma scanning and explicit whitespace trimming.

Workarounds

If upgrading is not possible, reject or remove oversized tracestate headers before trace-context extraction. This reduces the per-request parsing cost but does not eliminate the risk from repeated requests.