High
Security advisory
A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-33193
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 11:47 UTC · Revision 1
Source evidence
A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.
osv:CVE-2021-33193
Complete source record
{
"id": "3480e62ca528907af3cb7ff639d672094563a26f756d8bc90dd1d711bac12671",
"url": "https://osv.dev/vulnerability/CVE-2021-33193",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-33193",
"summary": "A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.",
"evidence": "osv:CVE-2021-33193",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2021-33193",
"aliases": [
"BIT-apache-2021-33193",
"CVE-2021-33193"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/apache/httpd",
"type": "GIT",
"events": [
{
"introduced": "47a9d8e8abf5697b4580c3ee2ade302b5c058fa6"
},
{
"fixed": "bbacd798d1494b5a99f4e3edab068ccc77b03b7e"
},
{
"fixed": "ecebcc035ccd8d0e2984fe41420d9e944f456b3c"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:apache:http_server:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "2.4.17"
},
{
"fixed": "2.4.49"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "ecebcc035ccd8d0e2984fe41420d9e944f456b3c"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-33193.json"
}
}
],
"modified": "2026-10-20T10:54:43.302745413Z",
"provider": "osv",
"references": [
"https://lists.debian.org/debian-lts-announce/2023/03/msg00002.html",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DSM6UWQICBJ2TU727RENU3HBKEAFLT6T/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EUVJVRJRBW5QVX4OY3NOHZDQ3B3YOTSG/",
"https://security.gentoo.org/glsa/202208-20",
"https://security.netapp.com/advisory/ntap-20210917-0004/",
"https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-apache-httpd-2.4.49-VWL69sWQ",
"https://www.tenable.com/security/tns-2021-17",
"https://github.com/apache/httpd/commit/ecebcc035ccd8d0e2984fe41420d9e944f456b3c.patch",
"https://lists.apache.org/thread.html/re4162adc051c1a0a79e7a24093f3776373e8733abaff57253fef341d%40%3Ccvs.httpd.apache.org%3E",
"https://lists.apache.org/thread.html/ree7519d71415ecdd170ff1889cab552d71758d2ba2904a17ded21a70%40%3Ccvs.httpd.apache.org%3E",
"https://www.oracle.com/security-alerts/cpuapr2022.html",
"https://www.oracle.com/security-alerts/cpujan2022.html",
"https://portswigger.net/research/http2"
],
"provider_metadata": {
"unresolved_ranges": [
{
"cpes": [
"cpe:2.3:a:oracle:secure_backup:*:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:secure_backup",
"extracted_events": [
{
"range": [
{
"fixed": "18.1.0.1.0"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:a:tenable:tenable.sc:*:*:*:*:*:*:*:*"
],
"vendor_product": "tenable:tenable.sc",
"extracted_events": [
{
"range": [
{
"last_affected": "5.19.1"
}
],
"source": "CPE_RANGE"
}
]
},
{
"cpes": [
"cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*"
],
"vendor_product": "debian:debian_linux",
"extracted_events": [
{
"range": [
{
"introduced": "10.0"
},
{
"last_affected": "10.0"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*",
"cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*"
],
"vendor_product": "fedoraproject:fedora",
"extracted_events": [
{
"range": [
{
"introduced": "34"
},
{
"last_affected": "34"
},
{
"introduced": "35"
},
{
"last_affected": "35"
}
],
"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-2021-33193",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 385994,
"published_at": "2021-08-16T08:15:11.48+00:00"
}