{"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"}}}}

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