datadog-opentelemetry has unbounded W3C tracestate parsing that may lead to DoS

Impact

Datadog tracing libraries that implement W3C Trace Context (tracecontext) propagation parse the incoming tracestate header without enforcing a size cap on the Datadog vendor entry (dd=...). The dd= value contains semicolon-separated key:value pairs, and the parser allocates a hash-map entry for each pair. A remote, unauthenticated attacker can send a tracestate header whose dd= member is arbitrarily large (or contains an arbitrarily large number of pairs), forcing unbounded CPU and memory consumption per request and enabling a remote Denial of Service. tracecontext extraction is enabled by default in affected tracers, so any internet-facing service instrumented with an affected version is exposed unless tracecontext has been explicitly removed from the propagation style configuration.

Patches

This is resolved in version 0.3.3 and later of the dd-trace-rs library.

Workarounds

If you cannot upgrade immediately: 1. Disable tracecontext extraction by setting DD_TRACE_PROPAGATION_STYLE_EXTRACT to a value that does not include tracecontext (for example, datadog). 2. Cap the maximum HTTP request header size at an upstream proxy or web server.