{
  "containers": {
    "cna": {
      "affected": [
        {
          "product": "h2o",
          "vendor": "h2o",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 4212ce114506a073505fd389db16ad2ba4e582a0"
            }
          ]
        }
      ],
      "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."
        }
      ],
      "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"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-770",
              "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-11-04T21:39:41.868Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "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"
        }
      ],
      "source": {
        "advisory": "GHSA-q342-qp8v-p44c",
        "discovery": "UNKNOWN"
      },
      "title": "h2o: heap exhaustion using capsules"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-55367",
    "datePublished": "2026-11-04T21:39:41.868Z",
    "dateReserved": "2026-06-16T18:57:40.180Z",
    "dateUpdated": "2026-11-04T21:39:41.868Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}