{"affected":[{"defaultStatus":"affected","ecosystem":"github","packageName":"libexpat/libexpat","product":"libexpat","source":"CNA: VulnCheck","vendor":"libexpat project","versions":[{"lessThanOrEqual":"2.8.3","status":"affected","version":"0","versionType":"semver"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AB0)","source":"ADP: siemens-SADP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518-4 PN/DP MFP (6ES7518-4AX00-1AC0)","source":"ADP: siemens-SADP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AB0)","source":"ADP: siemens-SADP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP (6ES7518-4FX00-1AC0)","source":"ADP: siemens-SADP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]},{"defaultStatus":"unknown","product":"SIPLUS S7-1500 CPU 1518-4 PN/DP MFP (6AG1518-4AX00-4AC0)","source":"ADP: siemens-SADP","vendor":"Siemens","versions":[{"lessThan":"*","status":"affected","version":"V3.1.7","versionType":"custom"}]}],"cveId":"CVE-2026-66046","cwes":["CWE-407"],"description":"Expat through 2.8.3 contains a denial of service vulnerability caused by quadratic algorithmic complexity in the storeAtts() function in xmlparse.c, where processing N specified attributes with non-normalized values triggers an O(N^2) linear scan of elementType->defaultAtts to determine CDATA status. A remote unauthenticated attacker can supply a single well-formed XML document of a few megabytes to an application parsing untrusted XML to cause excessive CPU consumption, resulting in denial of service without requiring authentication, external entity resolution, or non-default parser options.","epss":{"date":"2026-11-09","percentile":0.54957,"score":0.00742},"exploits":[],"kev":null,"metrics":[{"score":8.7,"severity":"high","source":"CNA: VulnCheck","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","version":"4.0"},{"score":7.5,"severity":"high","source":"CNA: VulnCheck","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}],"modifiedAt":1794314977975,"publishedAt":1787062205176,"references":[{"source":"CNA: VulnCheck","tags":["issue-tracking","patch"],"url":"https://github.com/libexpat/libexpat/pull/1321"},{"source":"CNA: VulnCheck","tags":["third-party-advisory"],"url":"https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity"},{"source":"ADP: siemens-SADP","tags":[],"url":"https://cert-portal.siemens.com/productcert/html/ssa-457936.html"}],"remediation":[{"kind":"fix","source":"CNA: VulnCheck","text":"The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches.","url":"https://github.com/libexpat/libexpat/pull/1321"}],"revision":"f721c9b5ca515c1e25a411b68e115a6669160059f0146c753ce83d18d3243a82","sources":[{"modifiedAt":1794314977975,"name":"CNA: VulnCheck","retrievedAt":1794316748669,"url":"https://www.cve.org/CVERecord?id=CVE-2026-66046"},{"modifiedAt":null,"name":"FIRST EPSS","retrievedAt":1794291558282,"url":"https://api.first.org/data/v1/epss?cve=CVE-2026-66046"}],"ssvc":{"assessedAt":1787233704577,"automatable":"yes","exploitation":"none","source":"ADP: CISA-ADP","technicalImpact":"partial"},"status":"published","title":"Expat Denial of Service via storeAtts() Quadratic Complexity","updatedAt":1794316748669}