What is CVE-2026-21726?

CVE-2026-21726 is a medium-severity vulnerability in Grafana Loki. CVSS score: 5.3/10. Published 2026-04-15.

How severe is CVE-2026-21726?

Medium severity. CVSS v3 base score is 5.3 out of 10.

Vulnerability in Grafana Loki

CVE-2026-21726

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 Su…

EPSS: 0.000 (4.2th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.

Affected products

Grafana Loki — versions 2.3.0

References

grafana.com/security/security-advisories/cve-2026-21726 (vendor-advisory)

Frequently asked questions

What is CVE-2026-21726?: CVE-2026-21726 is a medium-severity vulnerability in Grafana Loki. CVSS score: 5.3/10. Published 2026-04-15.
How severe is CVE-2026-21726?: Medium severity. CVSS v3 base score is 5.3 out of 10.