{"id":"CVE-2026-66046","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-66046","summary":"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…","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->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.","published":"2026-08-18T15:16:57.000","modified":"2026-08-18T15:16:57.000","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":null,"affectedPackages":[],"fix":{"url":"https://github.com/libexpat/libexpat/pull/1321","label":"libexpat/libexpat#1321"},"references":[{"type":"WEB","url":"https://github.com/libexpat/libexpat/pull/1321"},{"type":"WEB","url":"https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity"}],"provenance":{"sources":["OSV.dev","NVD","FIRST.org (EPSS)"],"lastVerified":"2026-08-18T15:16:57.000"}}