HighFix available
modsecurity, modsecurity-apache — security advisory
ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4.
- Products
- modsecurity, modsecurity-apache
- Affected versions
- 2.9.0-1, 2.9.1-3, 2.9.2-1, 2.9.3-1, 3.0.10-1, 3.0.11-1, 3.0.12-1, 3.0.12-1.1build1, 3.0.12-1.1build2, 3.0.13-1, 3.0.14-1, 3.0.14-1build1, 3.0.14-1build2, 3.0.15-1, 3.0.16-1, 3.0.3-1, 3.0.4-1, 3.0.4-1build1, 3.0.4-2, 3.0.6-1
- Fixed versions
- 2.9.0-1ubuntu0.1~esm1, 2.9.2-1ubuntu0.1~esm1, 2.9.3-1ubuntu0.1
- CVEs
- CVE-2021-42717
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 00:55 UTC · Revision 1
Source evidence
ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4.
osv:UBUNTU-CVE-2021-42717
modsecurity-apache
Fixed versions: 2.9.0-1ubuntu0.1~esm1
modsecurity-apache
Fixed versions: 2.9.2-1ubuntu0.1~esm1
modsecurity-apache
Fixed versions: 2.9.3-1ubuntu0.1
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
modsecurity
Fixed versions: Not specified
Complete source record
{
"id": "c39816856e1b368f5acb18c2c04a02fae9a1da5235a8450ffc1917639824f46a",
"url": "https://osv.dev/vulnerability/UBUNTU-CVE-2021-42717",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "UBUNTU-CVE-2021-42717",
"summary": "ModSecurity 3.x through 3.0.5 mishandles excessively nested JSON objects. Crafted JSON objects with nesting tens-of-thousands deep could result in the web server being unable to service legitimate requests. Even a moderately large (e.g., 300KB) HTTP request can occupy one of the limited NGINX worker processes for minutes and consume almost all of the available CPU on the machine. Modsecurity 2 is similarly vulnerable: the affected versions include 2.8.0 through 2.9.4.",
"evidence": "osv:UBUNTU-CVE-2021-42717",
"products": [
{
"name": {
"value": "modsecurity-apache",
"evidence": "/affected/0/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "2.9.0-1ubuntu0.1~esm1",
"evidence": "/affected/0/ranges"
}
],
"affected_versions": [
{
"value": "2.9.0-1",
"evidence": "/affected/0/versions"
}
]
},
{
"name": {
"value": "modsecurity-apache",
"evidence": "/affected/1/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "2.9.2-1ubuntu0.1~esm1",
"evidence": "/affected/1/ranges"
}
],
"affected_versions": [
{
"value": "2.9.1-3",
"evidence": "/affected/1/versions"
},
{
"value": "2.9.2-1",
"evidence": "/affected/1/versions"
}
]
},
{
"name": {
"value": "modsecurity-apache",
"evidence": "/affected/2/package/name"
},
"prerequisites": [],
"fixed_versions": [
{
"value": "2.9.3-1ubuntu0.1",
"evidence": "/affected/2/ranges"
}
],
"affected_versions": [
{
"value": "2.9.3-1",
"evidence": "/affected/2/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/3/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.3-1",
"evidence": "/affected/3/versions"
},
{
"value": "3.0.4-1",
"evidence": "/affected/3/versions"
},
{
"value": "3.0.4-1build1",
"evidence": "/affected/3/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/4/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.4-2",
"evidence": "/affected/4/versions"
},
{
"value": "3.0.6-1",
"evidence": "/affected/4/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/5/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.10-1",
"evidence": "/affected/5/versions"
},
{
"value": "3.0.11-1",
"evidence": "/affected/5/versions"
},
{
"value": "3.0.12-1",
"evidence": "/affected/5/versions"
},
{
"value": "3.0.12-1.1build1",
"evidence": "/affected/5/versions"
},
{
"value": "3.0.12-1.1build2",
"evidence": "/affected/5/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/6/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.13-1",
"evidence": "/affected/6/versions"
},
{
"value": "3.0.14-1",
"evidence": "/affected/6/versions"
},
{
"value": "3.0.14-1build1",
"evidence": "/affected/6/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/7/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.14-1build2",
"evidence": "/affected/7/versions"
},
{
"value": "3.0.15-1",
"evidence": "/affected/7/versions"
},
{
"value": "3.0.16-1",
"evidence": "/affected/7/versions"
}
]
},
{
"name": {
"value": "modsecurity",
"evidence": "/affected/8/package/name"
},
"prerequisites": [],
"fixed_versions": [],
"affected_versions": [
{
"value": "3.0.14-1build1",
"evidence": "/affected/8/versions"
},
{
"value": "3.0.14-1build2",
"evidence": "/affected/8/versions"
}
]
}
],
"severity": "high",
"structured": {
"id": "UBUNTU-CVE-2021-42717",
"aliases": [
"UBUNTU-CVE-2021-42717"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
},
{
"type": "Ubuntu",
"score": "medium"
}
],
"affected": [
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.9.0-1ubuntu0.1~esm1"
}
]
}
],
"package": {
"name": "modsecurity-apache",
"purl": "pkg:deb/ubuntu/modsecurity-apache?arch=source&distro=esm-apps%2Fxenial",
"ecosystem": "Ubuntu:Pro:16.04:LTS"
},
"versions": [
"2.9.0-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libapache2-mod-security2",
"binary_version": "2.9.0-1ubuntu0.1~esm1"
},
{
"binary_name": "libapache2-modsecurity",
"binary_version": "2.9.0-1ubuntu0.1~esm1"
}
],
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.9.2-1ubuntu0.1~esm1"
}
]
}
],
"package": {
"name": "modsecurity-apache",
"purl": "pkg:deb/ubuntu/modsecurity-apache?arch=source&distro=esm-apps%2Fbionic",
"ecosystem": "Ubuntu:Pro:18.04:LTS"
},
"versions": [
"2.9.1-3",
"2.9.2-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libapache2-mod-security2",
"binary_version": "2.9.2-1ubuntu0.1~esm1"
}
],
"availability": "Available with Ubuntu Pro: https://ubuntu.com/pro"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "2.9.3-1ubuntu0.1"
}
]
}
],
"package": {
"name": "modsecurity-apache",
"purl": "pkg:deb/ubuntu/modsecurity-apache?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"2.9.3-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libapache2-mod-security2",
"binary_version": "2.9.3-1ubuntu0.1"
}
],
"availability": "No subscription required"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=focal",
"ecosystem": "Ubuntu:20.04:LTS"
},
"versions": [
"3.0.3-1",
"3.0.4-1",
"3.0.4-1build1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3",
"binary_version": "3.0.4-1build1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=jammy",
"ecosystem": "Ubuntu:22.04:LTS"
},
"versions": [
"3.0.4-2",
"3.0.6-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3",
"binary_version": "3.0.6-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=noble",
"ecosystem": "Ubuntu:24.04:LTS"
},
"versions": [
"3.0.10-1",
"3.0.11-1",
"3.0.12-1",
"3.0.12-1.1build1",
"3.0.12-1.1build2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.12-1.1build2"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=questing",
"ecosystem": "Ubuntu:25.10"
},
"versions": [
"3.0.13-1",
"3.0.14-1",
"3.0.14-1build1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.14-1build1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
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],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=stonking",
"ecosystem": "Ubuntu:26.10"
},
"versions": [
"3.0.14-1build2",
"3.0.15-1",
"3.0.16-1"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.16-1"
}
]
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
}
]
}
],
"package": {
"name": "modsecurity",
"purl": "pkg:deb/ubuntu/modsecurity?arch=source&distro=resolute",
"ecosystem": "Ubuntu:26.04:LTS"
},
"versions": [
"3.0.14-1build1",
"3.0.14-1build2"
],
"database_specific": {
"source": "https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2021/UBUNTU-CVE-2021-42717.json"
},
"ecosystem_specific": {
"binaries": [
{
"binary_name": "libmodsecurity3t64",
"binary_version": "3.0.14-1build2"
}
]
}
}
],
"modified": "2026-10-17T12:56:15.846699234Z",
"provider": "osv",
"upstream": [
"CVE-2021-42717"
],
"references": [
"https://ubuntu.com/security/CVE-2021-42717",
"https://github.com/SpiderLabs/ModSecurity/issues/2647",
"https://ubuntu.com/security/notices/USN-6370-1",
"https://www.cve.org/CVERecord?id=CVE-2021-42717"
]
},
"related_cves": [
{
"value": "CVE-2021-42717",
"evidence": "/upstream"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 355072,
"published_at": "2021-12-07T22:15:00+00:00"
}