High
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
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-42717
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 07:55 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:CVE-2021-42717
Complete source record
{
"id": "6c228b0c9c598d5d4ddf9bf0377141502f109ea714253d5992a8b1257f68a9c0",
"url": "https://osv.dev/vulnerability/CVE-2021-42717",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "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:CVE-2021-42717",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2021-42717",
"aliases": [
"BIT-modsecurity-2021-42717",
"BIT-modsecurity2-2021-42717",
"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"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/owasp-modsecurity/ModSecurity",
"type": "GIT",
"events": [
{
"introduced": "c1cd668acb820824e791ba802396c60900eae9c1"
},
{
"fixed": "c3d7f4b560797a052681dcffb97a22bb906487cd"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.0.6"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"v3.0.5",
"v3.0.4",
"v3.0.3",
"v3.0.2",
"v3.0.1",
"v3.0.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-42717.json"
}
},
{
"ranges": [
{
"repo": "https://github.com/owasp-modsecurity/modsecurity",
"type": "GIT",
"events": [
{
"introduced": "c1cd668acb820824e791ba802396c60900eae9c1"
},
{
"fixed": "c3d7f4b560797a052681dcffb97a22bb906487cd"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:owasp:modsecurity:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "3.0.0"
},
{
"fixed": "3.0.6"
}
],
"source": "CPE_RANGE"
}
]
}
}
],
"versions": [
"v3.0.5",
"v3.0.4",
"v3.0.3",
"v3.0.2",
"v3.0.1",
"v3.0.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-42717.json"
}
}
],
"modified": "2026-10-24T10:31:00.473953022Z",
"provider": "osv",
"references": [
"https://lists.debian.org/debian-lts-announce/2022/05/msg00042.html",
"https://www.debian.org/security/2021/dsa-5023",
"https://www.oracle.com/security-alerts/cpuapr2022.html",
"https://www.trustwave.com/en-us/resources/blogs/spiderlabs-blog/modsecurity-dos-vulnerability-in-json-parsing-cve-2021-42717/"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:a:trustwave:modsecurity:*:*:*:*:*:*:*:*"
],
"vendor_product": "trustwave:modsecurity",
"extracted_events": [
{
"range": [
{
"introduced": "2.0.0"
},
{
"fixed": "2.9.5"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*",
"cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*",
"cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*"
],
"vendor_product": "debian:debian_linux",
"extracted_events": [
{
"range": [
{
"introduced": "9.0"
},
{
"last_affected": "9.0"
},
{
"introduced": "10.0"
},
{
"last_affected": "10.0"
},
{
"introduced": "11.0"
},
{
"last_affected": "11.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:f5:nginx_modsecurity_waf:r24:*:*:*:*:*:*:*",
"cpe:2.3:a:f5:nginx_modsecurity_waf:r25:*:*:*:*:*:*:*"
],
"vendor_product": "f5:nginx_modsecurity_waf",
"extracted_events": [
{
"range": [
{
"introduced": "r24"
},
{
"last_affected": "r24"
},
{
"introduced": "r25"
},
{
"last_affected": "r25"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:http_server:12.2.1.3.0:*:*:*:*:*:*:*",
"cpe:2.3:a:oracle:http_server:12.2.1.4.0:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:http_server",
"extracted_events": [
{
"range": [
{
"introduced": "12.2.1.3.0"
},
{
"last_affected": "12.2.1.3.0"
},
{
"introduced": "12.2.1.4.0"
},
{
"last_affected": "12.2.1.4.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:zfs_storage_appliance_kit:8.8:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:zfs_storage_appliance_kit",
"extracted_events": [
{
"range": [
{
"introduced": "8.8"
},
{
"last_affected": "8.8"
}
],
"source": "CPE_STRING"
}
]
}
]
}
},
"related_cves": [
{
"value": "CVE-2021-42717",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 439555,
"published_at": "2021-12-07T22:15:06.95+00:00"
}