{"id":"CVE-2026-86250","summary":"h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie","details":"h3 versions before 2.0.1-rc.18 fail to validate the chunk count parsed from user-controlled cookie values in setChunkedCookie() and deleteChunkedCookie() functions. Attackers can send a crafted cookie header with an extremely large chunk count to trigger an O(n²) cleanup loop that hangs the server process.","aliases":["GHSA-q5pr-72pq-83v3"],"modified":"2026-09-10T03:31:03.616866175Z","published":"2026-09-06T12:00:26.211Z","database_specific":{"cna_assigner":"VulnCheck","cwe_ids":["CWE-400"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86250.json"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86250.json"},{"type":"ADVISORY","url":"https://github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86250"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unbounded-chunked-cookie"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/h3js/h3","events":[{"introduced":"62356d7964d2640b6bf7bbba457732fe944ed618"},{"fixed":"cb70e1ba513be827bb3698127bb7d06467412911"}],"database_specific":{"extracted_events":[{"introduced":"2.0.0-beta.4"},{"fixed":"2.0.1-rc.18"},{"introduced":"0"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["v2.0.1-rc.17","v1.15.8","v2.0.1-rc.16","v2.0.1-rc.15","v2.0.1-rc.14","v2.0.1-rc.13","v2.0.1-rc.12","v2.0.1-rc.11","v2.0.1-rc.10","v2.0.1-rc.9","v2.0.1-rc.8","v2.0.1-rc.7","v2.0.1-rc.6","v2.0.1-rc.5","v2.0.1-rc.4","v2.0.1-rc.3","v2.0.1-rc.2","v2.0.0-rc.1","v2.0.0-beta.5","v2.0.0-beta.4"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-86250.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"}]}