OpenTelemetry JavaScript: Denial of service in `JaegerPropagator` via unhandled exception on a malformed header

Summary

@opentelemetry/propagator-jaeger decodes incoming HTTP header values with decodeURIComponent() without handling decode errors. A single request carrying a malformed percent-encoded value (for example a bare %) in an uber-trace-id or uberctx-* header throws an uncaught URIError, terminating any Node.js process that uses JaegerPropagator as its active propagator.

Impact

Denial of Service: Any unauthenticated remote attacker who can send an HTTP request to a service that has JaegerPropagator registered as the global propagator (e.g. via OTEL_PROPAGATORS=jaeger or propagation.setGlobalPropagator(new JaegerPropagator())) can terminate the process with a single request. Confidentiality and integrity are not affected.

Am I affected?

This issue affects only a specific, opt-in configuration. If you use OpenTelemetry's default propagators (W3C TraceContext and Baggage), you are not affected.

You are affected only if you have registered JaegerPropagator as the active propagator. Check for:

• @opentelemetry/propagator-jaeger in your dependency tree, and
• OTEL_PROPAGATORS set to jaeger (Jaeger only), or a direct propagation.setGlobalPropagator(new JaegerPropagator()) call in your code.

Note: if JaegerPropagator is combined with other propagators through a CompositePropagator (for example OTEL_PROPAGATORS=jaeger,tracecontext), the process does not terminate - the composite propagator catches the error - but affected requests silently fail to extract context. You should still upgrade.

Patched versions

• @opentelemetry/propagator-jaeger 2.9.0

Remediation

Update @opentelemetry/propagator-jaeger to 2.9.0 or later. The propagator now ignores header values it cannot decode instead of throwing.

Interim mitigation (if you cannot update): Trace-context headers should never be accepted unfiltered from untrusted callers. Until you can upgrade, strip or validate the uber-trace-id and uberctx-* headers on inbound requests at your edge - for example with a reverse proxy, API gateway, or load balancer (nginx, Envoy, etc.) - so that only trusted upstream services can set them.

Details

JaegerPropagator.extract() calls decodeURIComponent() on raw header values at two unguarded call sites: the uber-trace-id trace header and each uberctx-* baggage value. decodeURIComponent() throws URIError: URI malformed on invalid percent-encoding. Because the HTTP instrumentation extracts context before its request-handler error wrapper, and a single configured propagator is not wrapped in a CompositePropagator (which would otherwise catch the error), the exception propagates as an uncaughtException and terminates the process.

Proof of concept

Against a service using JaegerPropagator:

curl -H 'uberctx-user: %' http://target/
# or
curl -H 'uber-trace-id: %' http://target/

The Node.js process exits with URIError: URI malformed and subsequent requests are refused.