FKIE_CVE-2026-27824

Vulnerability from fkie_nvd - Published: 2026-02-27 20:21 - Updated: 2026-02-27 20:21
Severity ?
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-r7v8-2xrw
Impacted products
Vendor Product Version
To clipboard 

{
  "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."
    }
  ],
  "id": "CVE-2026-27824",
  "lastModified": "2026-02-27T20:21:39.973",
  "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"
      }
    ]
  },
  "published": "2026-02-27T20:21:39.973",
  "references": [
    {
      "source": "security-advisories@github.com",
      "url": "https://github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrw"
    }
  ],
  "sourceIdentifier": "security-advisories@github.com",
  "vulnStatus": "Received",
  "weaknesses": [
    {
      "description": [
        {
          "lang": "en",
          "value": "CWE-307"
        },
        {
          "lang": "en",
          "value": "CWE-346"
        }
      ],
      "source": "security-advisories@github.com",
      "type": "Primary"
    }
  ]
}


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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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