{"id":"CVE-2026-86250","state":"PUBLISHED","title":"h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie","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.","publishedAt":"2026-09-06T12:00:26.211Z","updatedAt":"2026-09-18T17:23:10.520Z","severity":{"score":8.7,"label":"High","version":"4.0","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","source":"VulnCheck"},"assigner":"VulnCheck","products":["h3js h3"],"affected":[{"vendor":"h3js","product":"h3","packageURL":"pkg:npm/h3","defaultStatus":"unaffected","versions":[{"version":"2.0.0-beta.4","status":"affected","lessThan":"2.0.1-rc.18","versionType":"semver"},{"version":"2.0.1-rc.18","status":"unaffected","versionType":"semver"}]}],"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"],"weaknesses":["CWE-400"],"ingestedAt":"2026-10-29T20:13:26.108Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/86xxx/CVE-2026-86250.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-86250","state":"PUBLISHED","datePublished":"2026-09-06T12:00:26.211Z","dateUpdated":"2026-09-18T17:23:10.520Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-09-06T11:35:19.316Z"},"containers":{"cna":{"title":"h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"h3js","product":"h3","packageURL":"pkg:npm/h3","defaultStatus":"unaffected","versions":[{"version":"2.0.0-beta.4","status":"affected","lessThan":"2.0.1-rc.18","versionType":"semver"},{"version":"2.0.1-rc.18","status":"unaffected","versionType":"semver"}]}],"references":[{"url":"https://github.com/h3js/h3/security/advisories/GHSA-q5pr-72pq-83v3","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-q5pr-72pq-83v3)"},{"url":"https://www.vulncheck.com/advisories/h3-before-2.0.1-rc.18-denial-of-service-via-unbounded-chunked-cookie","name":"VulnCheck Advisory: h3 before 2.0.1-rc.18 Denial of Service via Unbounded Chunked Cookie","tags":["third-party-advisory"]}],"metrics":[{"format":"CVSS","cvssV4_0":{"version":"4.0","vectorString":"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","attackVector":"NETWORK","attackComplexity":"LOW","attackRequirements":"NONE","privilegesRequired":"NONE","userInteraction":"NONE","vulnConfidentialityImpact":"NONE","vulnIntegrityImpact":"NONE","vulnAvailabilityImpact":"HIGH","subConfidentialityImpact":"NONE","subIntegrityImpact":"NONE","subAvailabilityImpact":"NONE","baseScore":8.7,"baseSeverity":"HIGH"}},{"format":"CVSS","cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"UNCHANGED","confidentialityImpact":"NONE","integrityImpact":"NONE","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-400","lang":"en","description":"Uncontrolled Resource Consumption","type":"CWE"}]}],"providerMetadata":{"shortName":"VulnCheck","orgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateUpdated":"2026-09-06T12:00:26.211Z"},"datePublic":"2026-03-21T00:00:00.000Z","credits":[{"lang":"en","value":"offset","type":"reporter"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","metrics":[{"other":{"type":"ssvc","content":{"id":"CVE-2026-86250","role":"CISA Coordinator","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"version":"2.0.3","timestamp":"2026-09-18T17:07:52.002310Z"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-18T17:23:10.520Z"}}]}}}