Medium [CVE-2026-59296] Line-protocol and log injection via unsanitized input allows metric and log spoofing

Using untrusted, non-normalized input as-is for metrics data (such as metric names, tag keys, or tag values) is a dangerous antipattern that general-purpose instrumentation should never perform.

When such unsafe instrumentation is used, the application becomes vulnerable to injection and spoofing attacks because micrometer-registry-statsd and micrometer-core do not sanitize newline characters (\n, \r) by default prior to this fix. * For the StatsD registry in micrometer-registry-statsd (when using the Datadog or Etsy flavor), because the StatsD protocol is newline-delimited, this allows for line-protocol injection (cross-metric spoofing). * For LoggingMeterRegistry in micrometer-core, because metric output is printed line-by-line to log files, this allows for both metric spoofing (if downstream log-metrics scrapers or parsers ingest the log lines as separate metrics) and general log spoofing.

Specifically, an application is vulnerable when all the following are true: * The application uses a vulnerable version of io.micrometer:micrometer-registry-statsd or io.micrometer:micrometer-core. * The application uses the Datadog or Etsy flavor of the StatsD registry, or uses LoggingMeterRegistry. * The application instruments meters using user-controlled, unvalidated input for metric names, tag keys, or tag values.