CVE-2026-21726: Grafana Loki Path Traversal - CVE-2021-36156 Bypass

April 15, 2026 (updated April 16, 2026)

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.

References

github.com/advisories/GHSA-497x-rrr9-68jp
github.com/grafana/loki
grafana.com/security/security-advisories/cve-2026-21726
nvd.nist.gov/vuln/detail/CVE-2026-21726

Code Behaviors & Features

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