{"id":"CVE-2026-66046","summary":"Expat Denial of Service via storeAtts() Quadratic Complexity","details":"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-\u003edefaultAtts 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.","modified":"2026-09-10T18:27:12.659110881Z","published":"2026-08-18T14:10:05.176Z","related":["openSUSE-SU-2026:11733-1"],"database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-407"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66046.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/66xxx/CVE-2026-66046.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66046"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity"},{"type":"REPORT","url":"https://github.com/libexpat/libexpat/pull/1321"},{"type":"PACKAGE","url":"https://github.com/libexpat/libexpat"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/libexpat/libexpat","events":[{"introduced":"0"},{"fixed":"92810461043fce37e70079b37ab1f04490a8f039"}],"database_specific":{"extracted_events":[{"introduced":"0"},{"last_affected":"2.8.3"},{"fixed":"2.8.3"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["R_2_8_2","R_2_8_1","R_2_8_0","R_2_7_5","R_2_7_4","R_2_7_3","R_2_7_2","R_2_7_1","R_2_7_0","R_2_6_4","R_2_6_3","R_2_6_2","R_2_6_1","R_2_6_0","R_2_5_0","R_2_4_9","R_2_4_8","R_2_4_7","R_2_4_6","R_2_4_5","R_2_4_4","R_2_4_3","R_2_4_2","R_2_4_1","R_2_4_0","R_2_3_0","R_2_2_10","R_2_2_9","R_2_2_8","R_2_2_7","R_2_2_6","R_2_2_5","R_2_2_4","R_2_2_3","R_2_2_2","R_2_2_1","R_2_2_0","R_2_1_1","R_2_1_0","R_2_0_1","R_2_0_0","R_1_95_8","R_1_95_7","R_1_95_6","R_1_95_5","R_1_95_4","R_1_95_3","R_1_95_2","R_1_95_0","libexpat-alpha-1","start","sourceforge_init","jclark-orig","V20000512","V19991013","V19990728","V19990709","V19990626","V1_1","V19990425","V1990307","V19990109","V19981231","V19981122","V1_0","beta4","beta3","beta2","REC1_0"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-66046.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}