{"id":"CVE-2021-43818","aliases":["GHSA-55x5-fj6c-h6m8","PYSEC-2021-852"],"title":"lxml's HTML Cleaner allows crafted and SVG embedded scripts to pass through","summary":"lxml's HTML Cleaner allows crafted and SVG embedded scripts to pass through","severity":"high","cvss":8.2,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:H/A:N","vendor":"lxml","product":"lxml","ecosystem":"pip","affected":["lxml < 4.6.5"],"patched":["lxml 4.6.5"],"published":"2021-12-13","updated":"2026-07-08","source":"OSV","sourceUrl":"https://osv.dev/vulnerability/GHSA-55x5-fj6c-h6m8","references":[{"url":"https://github.com/lxml/lxml/security/advisories/GHSA-55x5-fj6c-h6m8"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-43818"},{"url":"https://github.com/lxml/lxml/commit/12fa9669007180a7bb87d990c375cf91ca5b664a"},{"url":"https://github.com/lxml/lxml/commit/a3eacbc0dcf1de1c822ec29fb7d090a4b1712a9c#diff-59130575b4fb2932c957db2922977d7d89afb0b2085357db1a14615a2fcad776"},{"url":"https://github.com/lxml/lxml/commit/f2330237440df7e8f39c3ad1b1aa8852be3b27c0"},{"url":"https://www.oracle.com/security-alerts/cpujul2022.html"},{"url":"https://www.oracle.com/security-alerts/cpuapr2022.html"},{"url":"https://www.debian.org/security/2022/dsa-5043"},{"url":"https://security.netapp.com/advisory/ntap-20220107-0005"},{"url":"https://security.gentoo.org/glsa/202208-06"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/ZQ4SPKJX3RRJK4UWA6FXCRHD2TVRQI44"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/WZGNET2A4WGLSUXLBFYKNC5PXHQMI3I7"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/V2XMOM5PFT6U5AAXY6EFNT5JZCKKHK2V"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/TUIS2KE3HZ2AAQKXFLTJFZPP2IFHJTC7"},{"url":"https://lists.debian.org/debian-lts-announce/2021/12/msg00037.html"},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/lxml/PYSEC-2021-852.yaml"},{"url":"https://github.com/lxml/lxml"}],"tags":["osv","pip"],"epss":0.02477,"epssPercentile":0.83847,"ingestedAt":"2026-07-08T18:25:45.783Z","slug":"CVE-2021-43818","body":"## Overview\n\n### 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\n\n## Affected packages\n\n- `lxml < 4.6.5`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `lxml 4.6.5`","depth":"twilight","depthScore":46,"depthScoreParts":{"impact":45.1,"likelihood":0.5,"exploitation":0,"ransomware":0},"changes":[]}