{"id":"CVE-2026-44899","aliases":["GHSA-ccfx-mfmx-2fx9","PYSEC-2026-2209"],"url":"https://o3.security/vulnerability/CVE-2026-44899","summary":"Mistune Image Directive CSS Injection Vulnerability","details":"Mistune is a Python Markdown parser with renderers and plugins. Prior to 3.2.1, the Image directive plugin validates the :width: and :height: options with a regex compiled as _num_re = re.compile(r\"^\\d+(?:\\.\\d*)?\"). When the validated value is not a plain integer, render_block_image() inserts it directly into a style=\"width:...;\" or style=\"height:...;\" attribute. Because the value was accepted by the prefix-only regex, any CSS after the leading digits reaches the style= attribute verbatim and without escaping. This vulnerability is fixed in 3.2.1.","published":"2026-05-26T20:36:40.461Z","modified":"2026-08-12T03:51:45.909128522Z","cvss":{"score":4.7,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:N/A:N"},"epss":{"score":0.00228,"percentile":0.13687,"asOf":"2026-08-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"mistune","fixedVersion":"3.2.1"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/lepture/mistune/releases/tag/v3.2.1"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44899.json"},{"type":"ADVISORY","url":"https://github.com/lepture/mistune/security/advisories/GHSA-ccfx-mfmx-2fx9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-44899"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:45.909128522Z"}}