Unauthenticated file disclosure via double-encoded path traversal
Published Apr 15, 2026 · Updated Apr 15, 2026
Path traversal in Grafana Labs Grafana Loki 2.3.0 through 3.5.8 allows remote attackers to read server files through the Ruler API. The Ruler namespace handler checks for traversal after one URL decode, allowing a double-encoded path to be decoded again downstream and escape the rules directory. Loki provides no built-in authentication, although an external authenticating proxy can restrict network access to the affected endpoint.
Summary
What happened
Path traversal in Grafana Labs Grafana Loki 2.3.0 through 3.5.8 allows remote attackers to read server files through the Ruler API. The Ruler namespace handler checks for traversal after one URL decode, allowing a double-encoded path to be decoded again downstream and escape the rules directory. Loki provides no built-in authentication, although an external authenticating proxy can restrict network access to the affected endpoint.
The record
- CVE
- CVE-2026-21726
- Published
- Apr 15, 2026
- Updated
- Apr 15, 2026
- Vendor
- Grafana Labs
- Product
- Grafana Loki
- Classifications
- CWE-22, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 15, 2026CVE publishedPublication date reported by the CVE source.
- Apr 15, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=2.3.0 <3.5.9
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
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Technologies
Your stack
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Your stack
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