A user with Viewer permissions can use specially crafted requests to the Tempo and Loki data source plugins to reach unintended backend endpoints. Depending on the backend configuration this can expose data source credentials, leak internal responses, or trigger administrative actions on the configured backend.

Loki queries with large limits can cause large memory allocations which can impact the availability of the service, depending on its deployment strategy.

The CVE-2021-36156 fix validates the namespace parameter for path traversal sequences after a single URL decode, by double encoding, an attacker can read files at the Ruler API endpoint /loki/api/v1/rules/{namespace}

Thanks to Prasanth Sundararajan for reporting this vulnerability.

An issue was discovered in Grafana Loki through 2.2.1. The header value X-Scope-OrgID is used to construct file paths for rules files, and if crafted to conduct directory traversal such as ae ../../sensitive/path/in/deployment pathname, then Loki will attempt to parse a rules file at that location and include some of the contents in the error message.