FKIE_CVE-2026-27468

Vulnerability from fkie_nvd - Published: 2026-02-24 18:29 - Updated: 2026-02-26 15:36
Severity ?
8.2 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H
Summary
Mastodon is a free, open-source social network server based on ActivityPub. FASP registration requires manual approval by an administrator. In versions 4.4.0 through 4.4.13 and 4.5.0 through 4.5.6, actions performed by a FASP to subscribe to account/content lifecycle events or to backfill content did not check properly whether the FASP was actually approved. This only affects Mastodon servers that have opted in to testing the experimental FASP feature by setting the environment variable `EXPERIMENTAL_FEATURES` to a value including `fasp`. An attacker can make subscriptions and request content backfill without approval by an administrator. Done once, this leads to minor information leak of URIs that are publicly available anyway. But done several times this is a serious vector for DOS, putting pressure on the sidekiq worker responsible for the `fasp` queue. The fix is included in the 4.4.14 and 4.5.7 releases. Admins that are actively testing the experimental "fasp" feature should update their systems. Servers not using the experimental feature flag `fasp` are not affected.
References
security-advisories@github.comhttps://github.com/mastodon/mastodon/commit/6ba6285a73c3a8b281123814d45f534e3bcebb96Patch
security-advisories@github.comhttps://github.com/mastodon/mastodon/security/advisories/GHSA-qgmm-vr4c-ggjgVendor Advisory, Patch
Impacted products
Vendor Product Version
joinmastodon mastodon *
joinmastodon mastodon *
To clipboard 

{
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "F8A96B12-8C08-4A0C-88A8-B7B2B7AED3BF",
              "versionEndExcluding": "4.4.14",
              "versionStartIncluding": "4.4.0",
              "vulnerable": true
            },
            {
              "criteria": "cpe:2.3:a:joinmastodon:mastodon:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "65E9009A-6D3F-4758-8EAA-6D832F06F3F6",
              "versionEndExcluding": "4.5.7",
              "versionStartIncluding": "4.5.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "Mastodon is a free, open-source social network server based on ActivityPub. FASP registration requires manual approval by an administrator. In versions 4.4.0 through 4.4.13 and 4.5.0 through 4.5.6, actions performed by a FASP to subscribe to account/content lifecycle events or to backfill content did not check properly whether the FASP was actually approved. This only affects Mastodon servers that have opted in to testing the experimental FASP feature by setting the environment variable `EXPERIMENTAL_FEATURES` to a value including `fasp`. An attacker can make subscriptions and request content backfill without approval by an administrator. Done once, this leads to minor information leak of URIs that are publicly available anyway. But done several times this is a serious vector for DOS, putting pressure on the sidekiq worker responsible for the `fasp` queue. The fix is included in the 4.4.14 and 4.5.7 releases. Admins that are actively testing the experimental \"fasp\" feature should update their systems. Servers not using the experimental feature flag `fasp` are not affected."
    },
    {
      "lang": "es",
      "value": "Mastodon es un servidor de red social gratuito y de c\u00f3digo abierto basado en ActivityPub. El registro FASP requiere aprobaci\u00f3n manual por parte de un administrador. En las versiones 4.4.0 a 4.4.13 y 4.5.0 a 4.5.6, las acciones realizadas por un FASP para suscribirse a eventos del ciclo de vida de cuentas/contenido o para rellenar contenido (backfill) no verificaban correctamente si el FASP estaba realmente aprobado. Esto solo afecta a los servidores de Mastodon que han optado por probar la caracter\u00edstica experimental FASP configurando la variable de entorno \u0027EXPERIMENTAL_FEATURES\u0027 con un valor que incluya \u0027fasp\u0027. Un atacante puede realizar suscripciones y solicitar el rellenado de contenido (backfill) sin la aprobaci\u00f3n de un administrador. Hecho una vez, esto conduce a una fuga menor de informaci\u00f3n de URIs que de todos modos est\u00e1n disponibles p\u00fablicamente. Pero hecho varias veces, esto es un vector serio para DoS, ejerciendo presi\u00f3n sobre el worker de sidekiq responsable de la cola \u0027fasp\u0027. La soluci\u00f3n est\u00e1 incluida en las versiones 4.4.14 y 4.5.7. Los administradores que est\u00e1n probando activamente la caracter\u00edstica experimental \u0027fasp\u0027 deber\u00edan actualizar sus sistemas. Los servidores que no utilizan la bandera de caracter\u00edstica experimental \u0027fasp\u0027 no se ven afectados."
    }
  ],
  "id": "CVE-2026-27468",
  "lastModified": "2026-02-26T15:36:00.510",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "HIGH",
          "baseScore": 8.2,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "LOW",
          "integrityImpact": "NONE",
          "privilegesRequired": "NONE",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 4.2,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "cvssMetricV40": [
      {
        "cvssData": {
          "Automatable": "NOT_DEFINED",
          "Recovery": "NOT_DEFINED",
          "Safety": "NOT_DEFINED",
          "attackComplexity": "LOW",
          "attackRequirements": "PRESENT",
          "attackVector": "NETWORK",
          "availabilityRequirement": "NOT_DEFINED",
          "baseScore": 4.8,
          "baseSeverity": "MEDIUM",
          "confidentialityRequirement": "NOT_DEFINED",
          "exploitMaturity": "UNREPORTED",
          "integrityRequirement": "NOT_DEFINED",
          "modifiedAttackComplexity": "NOT_DEFINED",
          "modifiedAttackRequirements": "NOT_DEFINED",
          "modifiedAttackVector": "NOT_DEFINED",
          "modifiedPrivilegesRequired": "NOT_DEFINED",
          "modifiedSubAvailabilityImpact": "NOT_DEFINED",
          "modifiedSubConfidentialityImpact": "NOT_DEFINED",
          "modifiedSubIntegrityImpact": "NOT_DEFINED",
          "modifiedUserInteraction": "NOT_DEFINED",
          "modifiedVulnAvailabilityImpact": "NOT_DEFINED",
          "modifiedVulnConfidentialityImpact": "NOT_DEFINED",
          "modifiedVulnIntegrityImpact": "NOT_DEFINED",
          "privilegesRequired": "NONE",
          "providerUrgency": "NOT_DEFINED",
          "subAvailabilityImpact": "NONE",
          "subConfidentialityImpact": "NONE",
          "subIntegrityImpact": "NONE",
          "userInteraction": "NONE",
          "valueDensity": "NOT_DEFINED",
          "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X",
          "version": "4.0",
          "vulnAvailabilityImpact": "HIGH",
          "vulnConfidentialityImpact": "LOW",
          "vulnIntegrityImpact": "NONE",
          "vulnerabilityResponseEffort": "NOT_DEFINED"
        },
        "source": "security-advisories@github.com",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-02-24T18:29:33.660",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Patch"
      ],
      "url": "https://github.com/mastodon/mastodon/commit/6ba6285a73c3a8b281123814d45f534e3bcebb96"
    },
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Vendor Advisory",
        "Patch"
      ],
      "url": "https://github.com/mastodon/mastodon/security/advisories/GHSA-qgmm-vr4c-ggjg"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-862"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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