{"id":"CVE-2016-9909","aliases":["GHSA-v9v9-xffq-rwr4","PYSEC-2017-14"],"url":"https://o3.security/vulnerability/CVE-2016-9909","summary":"Improper Neutralization of Input During Web Page Generation in html5lib","details":"The serializer in html5lib before 0.99999999 might allow remote attackers to conduct cross-site scripting (XSS) attacks by leveraging mishandling of the < (less than) character in attribute values.","published":"2017-02-22T16:59:00.380Z","modified":"2026-10-20T10:49:04.200652390Z","cvss":{"score":6.1,"severity":"MEDIUM","vector":"CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N"},"epss":{"score":0.0216,"percentile":0.81325,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"html5lib","fixedVersion":"0.999999999"}],"fix":{"url":"https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7","label":"html5lib/html5lib-python@9b8d8eb"},"references":[{"type":"ADVISORY","url":"http://www.securityfocus.com/bid/95132"},{"type":"ADVISORY","url":"https://github.com/html5lib/html5lib-python/issues/11"},{"type":"ADVISORY","url":"https://github.com/html5lib/html5lib-python/issues/12"},{"type":"ADVISORY","url":"https://html5lib.readthedocs.io/en/latest/changes.html#b9"},{"type":"FIX","url":"http://www.openwall.com/lists/oss-security/2016/12/06/5"},{"type":"FIX","url":"http://www.openwall.com/lists/oss-security/2016/12/08/8"},{"type":"FIX","url":"https://github.com/html5lib/html5lib-python/commit/9b8d8eb5afbc066b7fac9390f5ec75e5e8a7cab7"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2016-9909"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-v9v9-xffq-rwr4"},{"type":"PACKAGE","url":"https://github.com/html5lib/html5lib-python"},{"type":"WEB","url":"https://github.com/pypa/advisory-database/tree/main/vulns/html5lib/PYSEC-2017-14.yaml"},{"type":"WEB","url":"https://web.archive.org/web/20161229134056/http://www.securityfocus.com/bid/95132"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-20T10:49:04.200652390Z"}}