Loki Path Traversal - CVE-2021-36156 Bypass

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Summary

CVECVE-2026-21726
StatePUBLISHED
AssignerGRAFANA
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-04-15 20:16:34 UTC
Updated2026-04-17 15:08:01 UTC
DescriptionThe 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.

Risk And Classification

Primary CVSS: v3.1 5.3 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

EPSS: 0.000090000 probability, percentile 0.008760000 (date 2026-04-17)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
3.1CNADECLARED5.3MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Grafana Loki affected 2.3.0 3.5.9 semver OnPrem

References

ReferenceSourceLinkTags
grafana.com/security/security-advisories/cve-2026-21726 [email protected] grafana.com
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