{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55367","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","state":"PUBLISHED","assignerShortName":"GitHub_M","dateReserved":"2026-06-16T18:57:40.180Z","datePublished":"2026-11-04T21:39:41.868Z","dateUpdated":"2026-11-05T20:01:20.480Z"},"containers":{"cna":{"title":"h2o: heap exhaustion using capsules","problemTypes":[{"descriptions":[{"cweId":"CWE-770","lang":"en","description":"CWE-770: Allocation of Resources Without Limits or Throttling","type":"CWE"}]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"HIGH","baseScore":7.5,"baseSeverity":"HIGH","confidentialityImpact":"NONE","integrityImpact":"NONE","privilegesRequired":"NONE","scope":"UNCHANGED","userInteraction":"NONE","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"}}],"references":[{"name":"https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c","tags":["x_refsource_CONFIRM"],"url":"https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c"},{"name":"https://github.com/h2o/h2o/pull/3754","tags":["x_refsource_MISC"],"url":"https://github.com/h2o/h2o/pull/3754"},{"name":"https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0","tags":["x_refsource_MISC"],"url":"https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0"}],"affected":[{"vendor":"h2o","product":"h2o","versions":[{"version":"< 4212ce114506a073505fd389db16ad2ba4e582a0","status":"affected"}]}],"providerMetadata":{"orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","shortName":"GitHub_M","dateUpdated":"2026-11-04T21:39:41.868Z"},"descriptions":[{"lang":"en","value":"h2o is an HTTP server with support for HTTP/1.x, HTTP/2 and HTTP/3. Prior to commit 4212ce114506a073505fd389db16ad2ba4e582a0, a client could send an incomplete CONNECT-UDP Capsule with an excessively large declared length, causing H2O to keep buffering received bytes without a per-Capsule limit while waiting for the remainder. Deployments that enabled proxy.connect-udp and accepted CONNECT-UDP requests could exhaust server memory and lose availability. This vulnerability is fixed with commit 4212ce114506a073505fd389db16ad2ba4e582a0."}],"source":{"advisory":"GHSA-q342-qp8v-p44c","discovery":"UNKNOWN"}},"adp":[{"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-11-05T19:59:16.316316Z","id":"CVE-2026-55367","options":[{"Exploitation":"none"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"title":"CISA ADP Vulnrichment","providerMetadata":{"orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","shortName":"CISA-ADP","dateUpdated":"2026-11-05T20:01:20.480Z"}}]}}