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CVE-2021-4026

Status: ModifiedMedium (4.3)—

bookstack is vulnerable to Improper Access Control

CVSS

Exploitation probability (EPSS)

EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).

Affected technologies (1)

Bookstackapp — Bookstack

CWEs

References

Raw JSON (NVD)

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{
  "id": "CVE-2021-4026",
  "cveTags": [],
  "metrics": {
    "cvssMetricV2": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "version": "2.0",
          "baseScore": 4,
          "accessVector": "NETWORK",
          "vectorString": "AV:N/AC:L/Au:S/C:P/I:N/A:N",
          "authentication": "SINGLE",
          "integrityImpact": "NONE",
          "accessComplexity": "LOW",
          "availabilityImpact": "NONE",
          "confidentialityImpact": "PARTIAL"
        },
        "acInsufInfo": false,
        "impactScore": 2.9,
        "baseSeverity": "MEDIUM",
        "obtainAllPrivilege": false,
        "exploitabilityScore": 8,
        "obtainUserPrivilege": false,
        "obtainOtherPrivilege": false,
        "userInteractionRequired": false
      }
    ],
    "cvssMetricV30": [
      {
        "type": "Secondary",
        "source": "security@huntr.dev",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.0",
          "baseScore": 6.5,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "HIGH"
        },
        "impactScore": 3.6,
        "exploitabilityScore": 2.8
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 4.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "LOW",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 2.8
      }
    ]
  },
  "affected": [
    {
      "source": "security@huntr.dev",
      "affectedData": [
        {
          "vendor": "bookstackapp",
          "product": "bookstackapp/bookstack",
          "versions": [
            {
              "status": "affected",
              "version": "unspecified",
              "lessThan": "21.11.2",
              "versionType": "custom"
            }
          ]
        }
      ]
    }
  ],
  "published": "2021-11-30T20:15:07.690",
  "references": [
    {
      "url": "https://github.com/bookstackapp/bookstack/commit/b4fa82e3298a15443ca40bff205b7a16a1031d92",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "security@huntr.dev"
    },
    {
      "url": "https://huntr.dev/bounties/c6dfa80d-43e6-4b49-95af-cc031bb66b1d",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "security@huntr.dev"
    },
    {
      "url": "https://github.com/bookstackapp/bookstack/commit/b4fa82e3298a15443ca40bff205b7a16a1031d92",
      "tags": [
        "Patch",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    },
    {
      "url": "https://huntr.dev/bounties/c6dfa80d-43e6-4b49-95af-cc031bb66b1d",
      "tags": [
        "Exploit",
        "Third Party Advisory"
      ],
      "source": "af854a3a-2127-422b-91ae-364da2661108"
    }
  ],
  "vulnStatus": "Modified",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security@huntr.dev",
      "description": [
        {
          "lang": "en",
          "value": "CWE-284"
        }
      ]
    },
    {
      "type": "Primary",
      "source": "nvd@nist.gov",
      "description": [
        {
          "lang": "en",
          "value": "CWE-863"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "bookstack is vulnerable to Improper Access Control"
    },
    {
      "lang": "es",
      "value": "bookstack es vulnerable  a un Control de Acceso Inapropiado"
    }
  ],
  "lastModified": "2026-06-17T04:18:54.967",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:bookstackapp:bookstack:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "F20610CF-F2B6-47E2-975A-394784440D3D",
              "versionEndExcluding": "21.11.2"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security@huntr.dev"
}