Treat OpenTelemetry Baggage as propagated context with its own trust boundary

Propagation does not automatically make a value a recorded span attribute or a trusted identity.

Source facts

OpenTelemetry Baggage is a separate key-value context store. Values become span, metric, or log attributes only when explicitly added. Automatic instrumentation can propagate Baggage in outbound requests, including to unintended third parties. The documentation also warns that Baggage has no built-in integrity check proving an item originated from the application.

Source: OpenTelemetry documentation — Baggage.

Applicability

Review Baggage propagation, explicit attribute recording and item integrity before trusting supplied context.

DSE recommendation

DSE recommends allowing only necessary, nonsensitive context keys and documenting where propagation may leave the organization’s boundary. Avoid putting credentials or unrestricted personal information into Baggage. Validate externally supplied values before using them for operational decisions, and never use them alone to authorize access. Decide explicitly which values should become recorded attributes and control their cardinality. Review outbound integrations because a harmless-looking context addition can travel farther than the service that introduced it.

Verification

With synthetic values in a test request, inspect intended downstream propagation and recorded attributes separately. Confirm unapproved keys are excluded and that third-party requests follow the documented boundary. Verify the application does not treat a forged Baggage value as authenticated identity or authorization evidence. Retain the approved key list and synthetic outbound-header observations beside the recorded attributes. Ask the application owner to demonstrate the separate authenticated identity decision when a deliberately forged Baggage key is supplied.

Official reference

OpenTelemetry documentation — Baggage. Reviewed October 20, 2026.