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CVE-2026-27824

Estado: AnalizadaMedia (5.3)—

calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.4.0, the calibre Content Server's brute-force protection mechanism uses a ban key derived from both `remote_addr` and the `X-Forwarded-For` header. Since the `X-Forwarded-For` header is read directly from the HTTP request without any validation or trusted-proxy configuration, an attacker can bypass IP-based bans by simply changing or adding this header, rendering the brute-force protection completely ineffective. This is particularly dangerous for calibre servers exposed to the internet, where brute-force protection is the primary defense against credential stuffing and password guessing attacks. Version 9.4.0 contains a fix for the issue.

CVSS

Probabilidad de explotación (EPSS)

EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).

Tecnologías afectadas (1)

Calibre-ebook — Calibre

CWE

Referencias

JSON original (NVD)

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{
  "id": "CVE-2026-27824",
  "cveTags": [],
  "metrics": {
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-27824",
          "role": "CISA Coordinator",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "version": "2.0.3",
          "timestamp": "2026-03-02T12:54:19.314863Z"
        }
      }
    ],
    "cvssMetricV31": [
      {
        "type": "Secondary",
        "source": "security-advisories@github.com",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      },
      {
        "type": "Primary",
        "source": "nvd@nist.gov",
        "cvssData": {
          "scope": "UNCHANGED",
          "version": "3.1",
          "baseScore": 5.3,
          "attackVector": "NETWORK",
          "baseSeverity": "MEDIUM",
          "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
          "integrityImpact": "NONE",
          "userInteraction": "NONE",
          "attackComplexity": "LOW",
          "availabilityImpact": "NONE",
          "privilegesRequired": "NONE",
          "confidentialityImpact": "LOW"
        },
        "impactScore": 1.4,
        "exploitabilityScore": 3.9
      }
    ]
  },
  "affected": [
    {
      "source": "security-advisories@github.com",
      "affectedData": [
        {
          "vendor": "kovidgoyal",
          "product": "calibre",
          "versions": [
            {
              "status": "affected",
              "version": "< 9.4.0"
            }
          ]
        }
      ]
    }
  ],
  "published": "2026-02-27T20:21:39.973",
  "references": [
    {
      "url": "https://github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrw",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "type": "Secondary",
      "source": "security-advisories@github.com",
      "description": [
        {
          "lang": "en",
          "value": "CWE-307"
        },
        {
          "lang": "en",
          "value": "CWE-346"
        }
      ]
    }
  ],
  "descriptions": [
    {
      "lang": "en",
      "value": "calibre is a cross-platform e-book manager for viewing, converting, editing, and cataloging e-books. Prior to version 9.4.0, the calibre Content Server's brute-force protection mechanism uses a ban key derived from both `remote_addr` and the `X-Forwarded-For` header. Since the `X-Forwarded-For` header is read directly from the HTTP request without any validation or trusted-proxy configuration, an attacker can bypass IP-based bans by simply changing or adding this header, rendering the brute-force protection completely ineffective. This is particularly dangerous for calibre servers exposed to the internet, where brute-force protection is the primary defense against credential stuffing and password guessing attacks. Version 9.4.0 contains a fix for the issue."
    },
    {
      "lang": "es",
      "value": "calibre es un gestor de libros electrónicos multiplataforma para ver, convertir, editar y catalogar libros electrónicos. Antes de la versión 9.4.0, el mecanismo de protección contra fuerza bruta del servidor de contenido de calibre utiliza una clave de prohibición derivada tanto de 'remote_addr' como del encabezado 'X-Forwarded-For'. Dado que el encabezado 'X-Forwarded-For' se lee directamente de la solicitud HTTP sin ninguna validación o configuración de proxy de confianza, un atacante puede eludir las prohibiciones basadas en IP simplemente cambiando o añadiendo este encabezado, lo que hace que la protección contra fuerza bruta sea completamente ineficaz. Esto es particularmente peligroso para los servidores de calibre expuestos a internet, donde la protección contra fuerza bruta es la defensa principal contra ataques de relleno de credenciales y adivinación de contraseñas. La versión 9.4.0 contiene una solución para el problema."
    }
  ],
  "lastModified": "2026-06-17T10:27:44.763",
  "configurations": [
    {
      "nodes": [
        {
          "negate": false,
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:calibre-ebook:calibre:*:*:*:*:*:*:*:*",
              "vulnerable": true,
              "matchCriteriaId": "3665E54E-5F8D-405A-BA97-8DD783962094",
              "versionEndExcluding": "9.4.0"
            }
          ],
          "operator": "OR"
        }
      ]
    }
  ],
  "sourceIdentifier": "security-advisories@github.com"
}