{"cve":"CVE-2026-86250","nvd":{"published":"2026-09-06T12:17:15.767","modified":"2026-09-18T18:17:18.657","status":"Awaiting Analysis","description":"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.","cvss_v4":{"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","score":8.7},"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5},"cwes":["CWE-400"],"references":["https://github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3","https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unbounded-chunked-cookie"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:52:03.409947763+00:00"},"epss":{"cve":"CVE-2026-86250","score":0.00488,"percentile":0.42015,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-q5pr-72pq-83v3","url":"https://osv.dev/vulnerability/GHSA-q5pr-72pq-83v3","summary":"H3: Unbounded Chunked Cookie Count in Session Cleanup Loop may Lead to Denial of Service","modified":"2026-10-01T00:00:05.804891230Z","packages":[{"ecosystem":"npm","name":"h3","purl":"pkg:npm/h3","ranges":[">=2.0.0-beta.4 <2.0.1-rc.18"],"fixed":["2.0.1-rc.18"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}