CVE-2026-21726 (GCVE-0-2026-21726)

Vulnerability from cvelistv5 – Published: 2026-04-15 19:24 – Updated: 2026-05-13 19:28
VLAI
Title
Loki Path Traversal - CVE-2021-36156 Bypass
Summary
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
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-22 - Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Assigner
References
Impacted products
Vendor Product Version
Grafana Loki Affected: 2.3.0 , < 3.5.9 (semver)
Create a notification for this product.
Date Public
2026-04-15 19:20
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-21726",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-04-15T20:01:24.769436Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "problemTypes": [
          {
            "descriptions": [
              {
                "cweId": "CWE-22",
                "description": "CWE-22 Improper Limitation of a Pathname to a Restricted Directory (\u0027Path Traversal\u0027)",
                "lang": "en",
                "type": "CWE"
              }
            ]
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-04-20T18:58:17.749Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "platforms": [
            "OnPrem"
          ],
          "product": "Loki",
          "vendor": "Grafana",
          "versions": [
            {
              "lessThan": "3.5.9",
              "status": "affected",
              "version": "2.3.0",
              "versionType": "semver"
            }
          ]
        }
      ],
      "datePublic": "2026-04-15T19:20:00.780Z",
      "descriptions": [
        {
          "lang": "en",
          "value": "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."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
            "version": "3.1"
          }
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-05-13T19:28:29.093Z",
        "orgId": "57da9224-a3e2-4646-9d0e-c4dc2e05e7da",
        "shortName": "GRAFANA"
      },
      "references": [
        {
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://grafana.com/security/security-advisories/cve-2026-21726"
        }
      ],
      "source": {
        "discovery": "BUG_BOUNTY"
      },
      "title": "Loki Path Traversal - CVE-2021-36156 Bypass",
      "x_generator": {
        "engine": "cvelib 1.8.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "57da9224-a3e2-4646-9d0e-c4dc2e05e7da",
    "assignerShortName": "GRAFANA",
    "cveId": "CVE-2026-21726",
    "datePublished": "2026-04-15T19:24:31.268Z",
    "dateReserved": "2026-01-05T09:26:06.215Z",
    "dateUpdated": "2026-05-13T19:28:29.093Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-21726",
      "date": "2026-06-05",
      "epss": "0.00017",
      "percentile": "0.04229"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-21726\",\"sourceIdentifier\":\"security@grafana.com\",\"published\":\"2026-04-15T20:16:34.177\",\"lastModified\":\"2026-04-20T20:08:40.723\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"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.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security@grafana.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"LOW\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"NONE\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-22\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:grafana:loki:*:*:*:*:*:*:*:*\",\"versionEndExcluding\":\"3.6.4\",\"matchCriteriaId\":\"4A927B56-3873-4166-8F65-6E312D898B03\"}]}]}],\"references\":[{\"url\":\"https://grafana.com/security/security-advisories/cve-2026-21726\",\"source\":\"security@grafana.com\",\"tags\":[\"Vendor Advisory\"]}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-21726\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"partial\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-04-15T20:01:24.769436Z\"}}}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-22\", \"description\": \"CWE-22 Improper Limitation of a Pathname to a Restricted Directory (\u0027Path Traversal\u0027)\"}]}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-04-15T20:01:29.185Z\"}}], \"cna\": {\"title\": \"Loki Path Traversal - CVE-2021-36156 Bypass\", \"source\": {\"discovery\": \"BUG_BOUNTY\"}, \"metrics\": [{\"cvssV3_1\": {\"version\": \"3.1\", \"baseScore\": 5.3, \"baseSeverity\": \"MEDIUM\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N\"}}], \"affected\": [{\"vendor\": \"Grafana\", \"product\": \"Loki\", \"versions\": [{\"status\": \"affected\", \"version\": \"2.3.0\", \"lessThan\": \"3.5.9\", \"versionType\": \"semver\"}], \"platforms\": [\"OnPrem\"], \"defaultStatus\": \"unaffected\"}], \"datePublic\": \"2026-04-15T19:20:00.780Z\", \"references\": [{\"url\": \"https://grafana.com/security/security-advisories/cve-2026-21726\", \"tags\": [\"vendor-advisory\"]}], \"x_generator\": {\"engine\": \"cvelib 1.8.0\"}, \"descriptions\": [{\"lang\": \"en\", \"value\": \"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.\"}], \"providerMetadata\": {\"orgId\": \"57da9224-a3e2-4646-9d0e-c4dc2e05e7da\", \"shortName\": \"GRAFANA\", \"dateUpdated\": \"2026-05-13T19:28:29.093Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-21726\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-05-13T19:28:29.093Z\", \"dateReserved\": \"2026-01-05T09:26:06.215Z\", \"assignerOrgId\": \"57da9224-a3e2-4646-9d0e-c4dc2e05e7da\", \"datePublished\": \"2026-04-15T19:24:31.268Z\", \"assignerShortName\": \"GRAFANA\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





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.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.