{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-121438","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","state":"PUBLISHED","assignerShortName":"VulnCheck","dateReserved":"2026-11-03T12:32:14.752Z","datePublished":"2026-11-03T14:28:29.879Z","dateUpdated":"2026-11-03T14:28:29.879Z"},"containers":{"cna":{"providerMetadata":{"orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","shortName":"VulnCheck","dateUpdated":"2026-11-03T14:28:29.879Z"},"datePublic":"2026-10-19T00:00:00.000Z","title":"Mistune before 3.3.3 Denial of Service via Balanced Bracket Link Parsing","descriptions":[{"lang":"en","value":"Mistune before 3.3.3 contains a denial of service vulnerability in InlineParser.parse_link that allows attackers to cause quadratic CPU growth by supplying balanced nested brackets. Attackers can submit crafted Markdown with thousands of nested bracket pairs not forming a valid link, triggering repeated _contains_nested_link scans that exhaust CPU in parsing applications."}],"problemTypes":[{"descriptions":[{"lang":"en","description":"Uncontrolled Resource Consumption","cweId":"CWE-400","type":"CWE"}]}],"affected":[{"vendor":"lepture","product":"mistune","defaultStatus":"unaffected","packageURL":"pkg:pypi/mistune","versions":[{"version":"0","status":"affected","versionType":"semver","lessThan":"3.3.3"},{"version":"3.3.3","status":"unaffected","versionType":"semver"}]}],"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:mistune_project:mistune:*:*:*:*:*:*:*:*","versionEndExcluding":"3.3.3"}]}]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"LOW","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":6.9,"baseSeverity":"MEDIUM"}},{"format":"CVSS","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"LOW","baseScore":5.3,"baseSeverity":"MEDIUM"}}],"references":[{"url":"https://github.com/lepture/mistune/security/advisories/GHSA-47p6-w2rc-5qf7","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-47p6-w2rc-5qf7)"},{"url":"https://github.com/lepture/mistune/commit/fe02f40faf091f86da9ed62c865f31e11da111d7","tags":["patch"],"name":"Patch Commit"},{"name":"VulnCheck Advisory: Mistune before 3.3.3 Denial of Service via Balanced Bracket Link Parsing","tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/mistune-before-3.3.3-denial-of-service-via-balanced-bracket-link-parsing"}],"credits":[{"lang":"en","value":"Str1ckl4nd","type":"reporter"}],"x_generator":{"engine":"vulncheck-endgame"}}}}