How severe is CVE-2026-21726?

CVE-2026-21726 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.

Is CVE-2026-21726 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-21726?

CVE-2026-21726 affects Grafana Loki. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-21726?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

Does CVE-2026-21726 have an EU (EUVD) identifier?

Yes. CVE-2026-21726 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23100.

When was CVE-2026-21726 published?

CVE-2026-21726 was published on 2026-04-15 and last updated on 2026-06-17.

CVE-2026-21726

CVE-2026-21726 is a medium-severity vulnerability in Grafana Loki with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
EPSS exploit prediction: 0% (34th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-23100
Weakness: CWE-22
Affected product: Grafana Loki
Published: 2026-04-15
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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 Sundararajan for reporting this vulnerability.
How severe is CVE-2026-21726?: CVE-2026-21726 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity none, and availability none.
Is CVE-2026-21726 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (34th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-21726?: CVE-2026-21726 affects Grafana Loki. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-21726?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
Does CVE-2026-21726 have an EU (EUVD) identifier?: Yes. CVE-2026-21726 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-23100.
When was CVE-2026-21726 published?: CVE-2026-21726 was published on 2026-04-15 and last updated on 2026-06-17.

References

https://grafana.com/security/security-advisories/cve-2026-21726

Affected products (1)

cpe:2.3:a:grafana:loki:*:*:*:*:*:*:*:*

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