{"id":"CVE-2026-4671","state":"PUBLISHED","title":"justhtml before 1.18.0 Denial of Service via CSS Selector","description":"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 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.","publishedAt":"2026-08-23T13:34:08.443Z","updatedAt":"2026-08-24T18:09:57.316Z","severity":{"score":8.7,"label":"High","version":"4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","source":"VulnCheck"},"assigner":"VulnCheck","products":["EmilStenstrom justhtml"],"affected":[{"vendor":"EmilStenstrom","product":"justhtml","packageURL":"pkg:pypi/justhtml","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.18.0","versionType":"semver"},{"version":"1.18.0","status":"unaffected","versionType":"semver"}]}],"references":["https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-r8cj-3554-33mr","https://www.vulncheck.com/advisories/justhtml-before-denial-of-service-via-css-selector"],"weaknesses":["CWE-400"],"ingestedAt":"2026-10-29T20:12:16.098Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/4xxx/CVE-2026-4671.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-4671","state":"PUBLISHED","datePublished":"2026-08-23T13:34:08.443Z","dateUpdated":"2026-08-24T18:09:57.316Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-03-23T19:00:14.383Z"},"containers":{"cna":{"title":"justhtml before 1.18.0 Denial of Service via CSS Selector","descriptions":[{"lang":"en","value":"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 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."}],"affected":[{"vendor":"EmilStenstrom","product":"justhtml","packageURL":"pkg:pypi/justhtml","defaultStatus":"unaffected","versions":[{"version":"0","status":"affected","lessThan":"1.18.0","versionType":"semver"},{"version":"1.18.0","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/EmilStenstrom/justhtml/security/advisories/GHSA-r8cj-3554-33mr","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-r8cj-3554-33mr)"},{"url":"https://www.vulncheck.com/advisories/justhtml-before-denial-of-service-via-css-selector","name":"VulnCheck Advisory: justhtml before 1.18.0 Denial of Service via CSS Selector","tags":["third-party-advisory"]}],"metrics":[{"cvssV4_0":{"Automatable":"NOT_DEFINED","Recovery":"NOT_DEFINED","Safety":"NOT_DEFINED","attackComplexity":"LOW","attackRequirements":"NONE","attackVector":"NETWORK","baseScore":8.7,"baseSeverity":"HIGH","exploitMaturity":"NOT_DEFINED","privilegesRequired":"NONE","providerUrgency":"NOT_DEFINED","subAvailabilityImpact":"NONE","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","userInteraction":"NONE","valueDensity":"NOT_DEFINED","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnerabilityResponseEffort":"NOT_DEFINED"},"format":"CVSS"},{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"format":"CVSS"}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"Uncontrolled Resource Consumption","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-08-23T13:34:08.443Z"},"datePublic":"2026-05-04T00:00:00.000Z","credits":[{"lang":"en","value":"EmilStenstrom","type":"coordinator"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-08-24T18:08:58.030472Z","id":"CVE-2026-4671","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-08-24T18:09:57.316Z"}}]}}}