UBUNTU-CVE-2026-27824 (CVE-2026-27824)
Vulnerability from osv_ubuntu – Published: 2026-02-27 20:21 – Updated: 2026-05-20 15:26 – Source website
VLAI
Details
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.
Severity
5.3 (Medium)
5.3 (Medium)
N/A (UNKNOWN)
References
{
"affected": [
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "2.55.0+dfsg-1ubuntu0.2"
},
{
"binary_name": "calibre-bin",
"binary_version": "2.55.0+dfsg-1ubuntu0.2"
}
]
},
"package": {
"ecosystem": "Ubuntu:16.04:LTS",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@2.55.0+dfsg-1ubuntu0.2?arch=source\u0026distro=xenial"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"2.33.0+dfsg-1build1",
"2.38.0+dfsg-1",
"2.45.0+dfsg-1",
"2.45.0+dfsg-1build1",
"2.48.0+dfsg-1",
"2.48.0+dfsg-1build1",
"2.54.0+dfsg-1",
"2.55.0+dfsg-1",
"2.55.0+dfsg-1ubuntu0.2"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "3.21.0+dfsg-1build1"
},
{
"binary_name": "calibre-bin",
"binary_version": "3.21.0+dfsg-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:18.04:LTS",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@3.21.0+dfsg-1build1?arch=source\u0026distro=bionic"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.7.0+dfsg-2",
"3.7.0+dfsg-2build1",
"3.12.0+dfsg-1",
"3.13.0+dfsg-1",
"3.14.0+dfsg-1",
"3.15.0.1+dfsg-1",
"3.16.0+dfsg-1",
"3.16.0+dfsg-1build1",
"3.17.0+dfsg-1",
"3.17.0+dfsg-2",
"3.18.0+dfsg-1build1",
"3.19.0+dfsg-1",
"3.20.0+dfsg-1",
"3.21.0+dfsg-1",
"3.21.0+dfsg-1build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "4.99.4+dfsg+really4.12.0-1ubuntu1"
},
{
"binary_name": "calibre-bin",
"binary_version": "4.99.4+dfsg+really4.12.0-1ubuntu1"
}
]
},
"package": {
"ecosystem": "Ubuntu:20.04:LTS",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@4.99.4+dfsg+really4.12.0-1ubuntu1?arch=source\u0026distro=focal"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"3.46.0+dfsg-1",
"4.2.0+dfsg-2",
"4.3.0+dfsg-1",
"4.3.0+dfsg-2",
"4.4.0+dfsg-1",
"4.5.0+dfsg-1",
"4.5.0+dfsg-2",
"4.5.0+dfsg-3",
"4.6.0+dfsg-1",
"4.7.0+dfsg-1",
"4.99.3+dfsg-2",
"4.99.4+dfsg-1",
"4.99.4+dfsg-1build1",
"4.99.4+dfsg+really4.10.0+py3-2",
"4.99.4+dfsg+really4.11.2-1",
"4.99.4+dfsg+really4.11.2-1build1",
"4.99.4+dfsg+really4.12.0-1",
"4.99.4+dfsg+really4.12.0-1build1",
"4.99.4+dfsg+really4.12.0-1ubuntu1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "5.37.0+dfsg-1build1"
},
{
"binary_name": "calibre-bin",
"binary_version": "5.37.0+dfsg-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:22.04:LTS",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@5.37.0+dfsg-1build1?arch=source\u0026distro=jammy"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"5.25.0+dfsg-2",
"5.33.2+dfsg-1",
"5.34.0+dfsg-1",
"5.35.0+dfsg-1ubuntu2",
"5.37.0+dfsg-1",
"5.37.0+dfsg-1build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "7.6.0+ds-1build1"
},
{
"binary_name": "calibre-bin",
"binary_version": "7.6.0+ds-1build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:24.04:LTS",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@7.6.0+ds-1build1?arch=source\u0026distro=noble"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"6.24.0+ds-1",
"6.29.0+ds-1",
"7.0.0+ds-1",
"7.1.0+ds-1",
"7.1.0+ds-2",
"7.2.0+ds-1",
"7.2.0+ds-1build1",
"7.3.0+ds-1",
"7.4.0+ds-1",
"7.5.1+ds-1",
"7.5.1+ds-2",
"7.5.1+ds-3",
"7.6.0+ds-1",
"7.6.0+ds-1build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "8.8.0+ds-3build1"
},
{
"binary_name": "calibre-bin",
"binary_version": "8.8.0+ds-3build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:25.10",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@8.8.0+ds-3build1?arch=source\u0026distro=questing"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"7.26.0+ds-4build1",
"8.3.0+ds-1",
"8.4.0+ds-1",
"8.5.0+ds-1",
"8.6.0+ds-1",
"8.7.0+ds-1",
"8.8.0+ds-2",
"8.8.0+ds-3",
"8.8.0+ds-3build1"
]
},
{
"ecosystem_specific": {
"binaries": [
{
"binary_name": "calibre",
"binary_version": "9.2.1+ds+~0.10.5-2build1"
},
{
"binary_name": "calibre-bin",
"binary_version": "9.2.1+ds+~0.10.5-2build1"
}
]
},
"package": {
"ecosystem": "Ubuntu:26.04:LTS",
"name": "calibre",
"purl": "pkg:deb/ubuntu/calibre@9.2.1+ds+~0.10.5-2build1?arch=source\u0026distro=resolute"
},
"ranges": [
{
"events": [
{
"introduced": "0"
}
],
"type": "ECOSYSTEM"
}
],
"versions": [
"8.8.0+ds-3build1",
"8.13.0+ds+~0.10.5-3",
"8.14.0+ds+~0.10.5-1",
"8.15.0+ds+~0.10.5-1",
"8.16.0+ds+~0.10.5-2",
"8.16.2+ds+~0.10.5-1",
"8.16.2+ds+~0.10.5-2",
"8.16.2+ds+~0.10.5-3",
"9.2.1+ds+~0.10.5-2build1"
]
}
],
"aliases": [],
"details": "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": "UBUNTU-CVE-2026-27824",
"modified": "2026-05-20T15:26:07Z",
"published": "2026-02-27T20:21:00Z",
"references": [
{
"type": "REPORT",
"url": "https://ubuntu.com/security/CVE-2026-27824"
},
{
"type": "REPORT",
"url": "https://www.cve.org/CVERecord?id=CVE-2026-27824"
},
{
"type": "REPORT",
"url": "https://github.com/kovidgoyal/calibre/security/advisories/GHSA-vhxc-r7v8-2xrw"
}
],
"related": [],
"schema_version": "1.7.0",
"severity": [
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N",
"type": "CVSS_V3"
},
{
"score": "medium",
"type": "Ubuntu"
}
],
"upstream": [
"CVE-2026-27824"
]
}
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Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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