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FKIE_CVE-2026-27824

Vulnerability from fkie_nvd - Published: 2026-02-27 20:21 - Updated: 2026-06-17 10:27
Severity
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
5.3 (Medium) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Summary
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.
References
security-advisories@github.comhttps://github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrwExploit, Vendor Advisory
Impacted products
Vendor Product Version
calibre-ebook calibre *
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "calibre",
          "vendor": "kovidgoyal",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 9.4.0"
            }
          ]
        }
      ],
      "source": "security-advisories@github.com"
    }
  ],
  "configurations": [
    {
      "nodes": [
        {
          "cpeMatch": [
            {
              "criteria": "cpe:2.3:a:calibre-ebook:calibre:*:*:*:*:*:*:*:*",
              "matchCriteriaId": "3665E54E-5F8D-405A-BA97-8DD783962094",
              "versionEndExcluding": "9.4.0",
              "vulnerable": true
            }
          ],
          "negate": false,
          "operator": "OR"
        }
      ]
    }
  ],
  "cveTags": [],
  "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\u0027s 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 electr\u00f3nicos multiplataforma para ver, convertir, editar y catalogar libros electr\u00f3nicos. Antes de la versi\u00f3n 9.4.0, el mecanismo de protecci\u00f3n contra fuerza bruta del servidor de contenido de calibre utiliza una clave de prohibici\u00f3n derivada tanto de \u0027remote_addr\u0027 como del encabezado \u0027X-Forwarded-For\u0027. Dado que el encabezado \u0027X-Forwarded-For\u0027 se lee directamente de la solicitud HTTP sin ninguna validaci\u00f3n o configuraci\u00f3n de proxy de confianza, un atacante puede eludir las prohibiciones basadas en IP simplemente cambiando o a\u00f1adiendo este encabezado, lo que hace que la protecci\u00f3n contra fuerza bruta sea completamente ineficaz. Esto es particularmente peligroso para los servidores de calibre expuestos a internet, donde la protecci\u00f3n contra fuerza bruta es la defensa principal contra ataques de relleno de credenciales y adivinaci\u00f3n de contrase\u00f1as. La versi\u00f3n 9.4.0 contiene una soluci\u00f3n para el problema."
    }
  ],
  "id": "CVE-2026-27824",
  "lastModified": "2026-06-17T10:27:44.763",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "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:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "security-advisories@github.com",
        "type": "Secondary"
      },
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "NETWORK",
          "availabilityImpact": "NONE",
          "baseScore": 5.3,
          "baseSeverity": "MEDIUM",
          "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:N",
          "version": "3.1"
        },
        "exploitabilityScore": 3.9,
        "impactScore": 1.4,
        "source": "nvd@nist.gov",
        "type": "Primary"
      }
    ],
    "ssvcV203": [
      {
        "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
        "ssvcData": {
          "id": "CVE-2026-27824",
          "options": [
            {
              "exploitation": "poc"
            },
            {
              "automatable": "no"
            },
            {
              "technicalImpact": "partial"
            }
          ],
          "role": "CISA Coordinator",
          "timestamp": "2026-03-02T12:54:19.314863Z",
          "version": "2.0.3"
        }
      }
    ]
  },
  "published": "2026-02-27T20:21:39.973",
  "references": [
    {
      "source": "security-advisories@github.com",
      "tags": [
        "Exploit",
        "Vendor Advisory"
      ],
      "url": "https://github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrw"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Analyzed",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-307"
        },
        {
          "lang": "en",
          "value": "CWE-346"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Secondary"
    }
  ]
}



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