{"id":"CVE-2026-4671","title":"justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification","summary":"justhtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings (via query(), matches(), or selector-based transfo…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-400"],"vendor":"justhtml","product":"justhtml","affected":["justhtml < 1.18.0"],"patched":["justhtml 1.18.0"],"published":"2026-08-23","updated":"2026-10-12","sourceUpdated":"2026-10-12T16:10:00.220","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-4671","references":[{"url":"https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-r8cj-3554-33mr","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/justhtml-before-denial-of-service-via-css-selector","label":"disclosure@vulncheck.com"},{"url":"https://github.com/EmilStenstrom/justhtml"}],"tags":["nvd","osv","pip"],"epss":0.00652,"epssPercentile":0.51014,"aliases":["GHSA-r8cj-3554-33mr"],"ecosystem":"pip","ingestedAt":"2026-08-24T19:25:44.327Z","slug":"CVE-2026-4671","body":"## Overview\n\njusthtml before 1.18.0 contains multiple low-severity denial-of-service issues in CSS selector handling and linkification. Applications that evaluate attacker-controlled selector strings (via query(), matches(), or selector-based transforms), run selector matching over very large untrusted documents, construct DOM trees from untrusted structure, or enable linkification over attacker-controlled text may consume disproportionate CPU or memory. Triggers include oversized selectors, large selector lists, oversized compound selectors, long combinator chains, deeply nested functional pseudo-classes, repeated token/positional matching, cyclic DOM graphs causing non-terminating traversal, and punctuation-heavy or trailing-bracket linkification input. These are availability-only concerns and do not by themselves allow script execution, data disclosure, or sanitizer bypass. Default JustHTML(sanitize=True) usage is not expected to be exposed, since selectors are normally supplied by application code.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Package advisory (CVE-2026-4671)\n\nAffected packages:\n\n- `justhtml < 1.18.0`\n\nPatched in:\n\n- `justhtml 1.18.0`\n\nSource: https://osv.dev/vulnerability/GHSA-r8cj-3554-33mr","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[{"seq":219480,"id":"CVE-2026-4671","ts":1791824359498,"field":"cvss","old":null,"new":"7.5"},{"seq":219479,"id":"CVE-2026-4671","ts":1791824359498,"field":"severity","old":"low","new":"high"}]}