---
id: CVE-2026-21726
aliases:
  - GHSA-497x-rrr9-68jp
  - GO-2026-5115
title: Grafana Loki Path Traversal - CVE-2021-36156 Bypass
summary: Grafana Loki Path Traversal - CVE-2021-36156 Bypass
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N'
vendor: grafana
product: github.com/grafana/loki/v3
ecosystem: go
affected:
  - github.com/grafana/loki/v3 < 3.6.4
patched:
  - github.com/grafana/loki/v3 3.6.4
published: '2026-04-15'
updated: '2026-09-10'
sourceUpdated: '2026-09-10T03:51:00.938890119Z'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-497x-rrr9-68jp'
references:
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2026-21726'
  - url: 'https://github.com/grafana/loki'
  - url: 'https://grafana.com/security/security-advisories/cve-2026-21726'
  - url: 'https://github.com/advisories/GHSA-497x-rrr9-68jp'
tags:
  - osv
  - go
epss: 0.00409
epssPercentile: 0.32375
ingestedAt: '2026-07-09T18:56:37.049Z'
---

## Overview

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.

## Affected packages

- `github.com/grafana/loki/v3 < 3.6.4`

## Remediation

Upgrade to a patched release:

- `github.com/grafana/loki/v3 3.6.4`