{"id":"CVE-2026-66046","title":"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) li…","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 with non-normalized values triggers an O(N^2) li…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-407"],"vendor":"libexpat_project","product":"libexpat","affected":["libexpat <= 2.8.3"],"published":"2026-08-18","updated":"2026-09-18","sourceUpdated":"2026-09-18T15:07:24.370","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-66046","references":[{"url":"https://github.com/libexpat/libexpat/pull/1321","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/expat-denial-of-service-via-storeatts-quadratic-complexity","label":"disclosure@vulncheck.com"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66046.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-66046"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2517901"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-66046"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66046"},{"url":"https://access.redhat.com/errata/RHSA-2026:65568"},{"url":"https://access.redhat.com/errata/RHSA-2026:74001"},{"url":"https://access.redhat.com/errata/RHSA-2026:72663"},{"url":"https://access.redhat.com/errata/RHSA-2026:72448"},{"url":"https://access.redhat.com/errata/RHSA-2026:79357"}],"tags":["nvd","csaf","vex","red-hat","cve.org"],"epss":0.00742,"epssPercentile":0.5447,"ingestedAt":"2026-09-18T14:43:13.027Z","patched":["hardened_images"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-08-20T13:48:24.577412Z"},"slug":"CVE-2026-66046","body":"## Overview\n\nExpat 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.\n\n## Affected\n\n- `libexpat <= 2.8.3`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **RHSA-2026:65568** · Red Hat · fixed in: Red Hat Hardened Images · released 2026-09-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:65568)\n- **Red Hat VEX** · Important · affected: Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, Red Hat Enterprise Linux 9, Red Hat OpenShift Container Platform 4 · no fix planned: Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 7, Red Hat Enterprise Linux 8, … · updated 2026-10-09 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-66046.json)\n- **RHSA-2026:74001** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 10), Red Hat Enterprise Linux BaseOS (v. 10) · released 2026-09-30 · [advisory](https://access.redhat.com/errata/RHSA-2026:74001)\n- **RHSA-2026:72663** · Red Hat · fixed in: Red Hat Enterprise Linux AppStream (v. 9), Red Hat Enterprise Linux BaseOS (v. 9) · released 2026-09-29 · [advisory](https://access.redhat.com/errata/RHSA-2026:72663)\n- **RHSA-2026:72448** · Red Hat · fixed in: Red Hat Enterprise Linux BaseOS (v. 8) · released 2026-09-28 · [advisory](https://access.redhat.com/errata/RHSA-2026:72448)\n- **RHSA-2026:79357** · Red Hat · fixed in: Red Hat Cost Management On-Premise 1 · released 2026-10-08 · [advisory](https://access.redhat.com/errata/RHSA-2026:79357)","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}