GHSA-497X-RRR9-68JP

Vulnerability from github – Published: 2026-04-15 21:30 – Updated: 2026-04-16 21:42
VLAI
Summary
Grafana Loki Path Traversal - CVE-2021-36156 Bypass
Details

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.

Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/grafana/loki/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "3.6.4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-21726"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-22",
      "CWE-601"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-16T21:42:00Z",
    "nvd_published_at": "2026-04-15T20:16:34Z",
    "severity": "MODERATE"
  },
  "details": "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}\n\nThanks to Prasanth Sundararajan for reporting this vulnerability.",
  "id": "GHSA-497x-rrr9-68jp",
  "modified": "2026-04-16T21:42:00Z",
  "published": "2026-04-15T21:30:18Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-21726"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/grafana/loki"
    },
    {
      "type": "WEB",
      "url": "https://grafana.com/security/security-advisories/cve-2026-21726"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Grafana Loki Path Traversal - CVE-2021-36156 Bypass"
}


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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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Nomenclature

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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.