OpenTelemetry, also known as OTel for short, is a vendor-neutral open-source Observability framework for instrumenting, generating, collecting, and exporting telemetry data such as traces, metrics, logs. Autoinstrumentation out of the box adds the label http_method that has unbound cardinality. It leads to the server's potential memory exhaustion when many malicious requests are sent.

HTTP method for requests can be easily set by an attacker to be random and long. In order to be affected program has to be instrumented for HTTP handlers and does not filter any unknown HTTP methods on the level of CDN, LB, previous middleware, etc. This issue has been patched in version 0.41b0.