{"id":"CVE-2021-43818","aliases":["GHSA-55x5-fj6c-h6m8","PYSEC-2021-852"],"url":"https://o3.security/vulnerability/CVE-2021-43818","summary":"lxml's HTML Cleaner allows crafted and SVG embedded scripts to pass through","details":"### Impact\nThe HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs.\n\nUsers that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5.\n\n### Patches\nThe issue has been resolved in lxml 4.6.5.\n\n### Workarounds\nNone.\n\n### References\nThe issues are tracked under the report IDs GHSL-2021-1037 and GHSL-2021-1038.\n","published":"2021-12-13T18:15:08.387Z","modified":"2026-07-08T06:27:22.488009342Z","cvss":{"score":7.1,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L"},"epss":{"score":0.02477,"percentile":0.83226,"asOf":"2026-08-23"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"lxml","fixedVersion":"4.6.5"}],"fix":{"url":"https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a","label":"lxml/lxml@12fa966"},"references":[{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7/"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44/"},{"type":"ADVISORY","url":"https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8"},{"type":"ADVISORY","url":"https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html"},{"type":"ADVISORY","url":"https://security.gentoo.org/glsa/202208-06"},{"type":"ADVISORY","url":"https://security.netapp.com/advisory/ntap-20220107-0005/"},{"type":"ADVISORY","url":"https://www.debian.org/security/2022/dsa-5043"},{"type":"FIX","url":"https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a"},{"type":"FIX","url":"https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776"},{"type":"FIX","url":"https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0"},{"type":"FIX","url":"https://www.oracle.com/security-alerts/cpuapr2022.html"},{"type":"FIX","url":"https://www.oracle.com/security-alerts/cpujul2022.html"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43818"},{"type":"WEB","url":"https://security.netapp.com/advisory/ntap-20220107-0005"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V"},{"type":"WEB","url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/lxml/PYSEC-2021-852.yaml"},{"type":"PACKAGE","url":"https://github.com/lxml/lxml"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-08T06:27:22.488009342Z"}}