High
Security advisory
lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. Users that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5 to receive a patch. There are no known workarounds available.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-43818
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 12:01 UTC · Revision 1
Source evidence
lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. Users that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5 to receive a patch. There are no known workarounds available.
osv:CVE-2021-43818
Complete source record
{
"id": "d9fc99520216b6cdcca8efa3b09f22682c74c651ae3260d6116073e9ce38c4bd",
"url": "https://osv.dev/vulnerability/CVE-2021-43818",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-43818",
"summary": "lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. Users that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5 to receive a patch. There are no known workarounds available.",
"evidence": "osv:CVE-2021-43818",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2021-43818",
"aliases": [
"CVE-2021-43818",
"GHSA-55x5-fj6c-h6m8",
"PYSEC-2021-852"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/lxml/lxml",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "a9611ba80bc5196c1dd07a0b1964fcb603695d63"
},
{
"fixed": "12fa9669007180a7bb87d990c375cf91ca5b664a"
},
{
"fixed": "a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c"
},
{
"fixed": "f2330237440df7e8f39c3ad1b1aa8852be3b27c0"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:lxml:lxml:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "0"
},
{
"fixed": "4.6.5"
}
],
"source": "CPE_RANGE"
},
{
"range": [
{
"fixed": "12fa9669007180a7bb87d990c375cf91ca5b664a"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "f2330237440df7e8f39c3ad1b1aa8852be3b27c0"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"lxml-4.6.4-5",
"lxml-4.6.4-4",
"lxml-4.6.4-3",
"lxml-4.6.4-2",
"lxml-4.6.4-1",
"lxml-4.6.4",
"lxml-4.6.3",
"lxml-4.6.2",
"lxml-4.6.1",
"lxml-4.6.0",
"lxml-4.5.2",
"lxml-4.5.1",
"lxml-4.5.0",
"lxml-4.4.1",
"lxml-4.4.0",
"lxml-4.3.2",
"lxml-4.3.1",
"lxml-4.3.0",
"lxml-4.2.2",
"lxml-4.2.1",
"lxml-4.2.0",
"lxml-4.1.1",
"lxml-4.1.0",
"lxml-4.0.0",
"lxml-3.8.0-py27fix",
"lxml-3.8.0",
"lxml-3.7.2",
"lxml-3.7.1",
"lxml-3.7.0",
"lxml-3.6.1",
"lxml-3.6.0",
"lxml-3.5.0",
"lxml-3.5.0b1",
"lxml-3.4.1",
"lxml-3.4.0",
"lxml-3.4.0beta1",
"lxml-3.3.3",
"lxml-3.3.2",
"lxml-3.3.1",
"lxml-3.3.0",
"lxml-3.3.0beta5",
"lxml-3.3.0beta4",
"lxml-3.3.0beta3",
"lxml-3.3.0beta2",
"lxml-3.3.0beta1",
"lxml-3.2.3",
"lxml-3.2.2",
"lxml-3.2.1",
"lxml-3.2.0",
"lxml-3.1.1",
"lxml-3.1.0",
"lxml-3.1beta1",
"lxml-3.0.1",
"lxml-3.0",
"lxml-3.0beta1",
"lxml-3.0alpha2",
"lxml-3.0alpha1",
"lxml-2.3.1",
"lxml-2.3",
"lxml-2.3beta1",
"lxml-2.3alpha2",
"lxml-2.3alpha1",
"lxml-2.2.2",
"lxml-2.2.1",
"lxml-2.2",
"lxml-2.1",
"lxml-2.1beta3",
"lxml-2.1beta2",
"lxml-2.1beta1",
"lxml-2.1alpha1",
"lxml-2.0.1",
"lxml-2.0",
"lxml-2.0beta2",
"lxml-2.0beta1",
"lxml-2.0alpha6",
"lxml-2.0alpha5",
"lxml-2.0alpha4",
"lxml-2.0alpha3",
"lxml-2.0alpha2",
"lxml-2.0alpha1",
"lxml-1.2",
"lxml-1.1",
"lxml-1.1beta",
"lxml-1.1alpha",
"lxml-1.0",
"lxml-1.0.beta",
"lxml-0.9",
"lxml-0.7",
"lxml-0.6",
"lxml-0.5.1"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-43818.json"
}
}
],
"modified": "2026-10-20T10:55:04.669571049Z",
"provider": "osv",
"references": [
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/",
"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44/",
"https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8",
"https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html",
"https://security.gentoo.org/glsa/202208-06",
"https://security.netapp.com/advisory/ntap-20220107-0005/",
"https://www.debian.org/security/2022/dsa-5043",
"https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a",
"https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776",
"https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0",
"https://www.oracle.com/security-alerts/cpuapr2022.html",
"https://www.oracle.com/security-alerts/cpujul2022.html"
],
"provider_metadata": {
"unresolved_ranges": [
{
"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: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:communications_cloud_native_core_binding_support_function:22.1.3:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:communications_cloud_native_core_binding_support_function",
"extracted_events": [
{
"range": [
{
"introduced": "22.1.3"
},
{
"last_affected": "22.1.3"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:communications_cloud_native_core_network_exposure_function:22.1.1:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:communications_cloud_native_core_network_exposure_function",
"extracted_events": [
{
"range": [
{
"introduced": "22.1.1"
},
{
"last_affected": "22.1.1"
}
],
"source": "CPE_STRING"
}
]
},
{
"cpes": [
"cpe:2.3:a:oracle:communications_cloud_native_core_policy:22.2.0:*:*:*:*:*:*:*"
],
"vendor_product": "oracle:communications_cloud_native_core_policy",
"extracted_events": [
{
"range": [
{
"introduced": "22.2.0"
},
{
"last_affected": "22.2.0"
}
],
"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-2021-43818",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 386840,
"published_at": "2021-12-13T18:15:08.387+00:00"
}