{"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": "2026-11-04T21:39:41.868Z"}, "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"}}}}

{}

{"affected": [{"affectedData": [{"product": "h2o", "vendor": "h2o", "versions": [{"status": "affected", "version": "< 4212ce114506a073505fd389db16ad2ba4e582a0"}]}], "source": "security-advisories@github.com"}], "cveTags": [], "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."}], "id": "CVE-2026-55367", "lastModified": "2026-11-04T22:18:06.167", "metrics": {"cvssMetricV31": [{"cvssData": {"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"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "security-advisories@github.com", "type": "Secondary"}]}, "published": "2026-11-04T22:18:06.167", "references": [{"source": "security-advisories@github.com", "url": "https://github.com/h2o/h2o/commit/4212ce114506a073505fd389db16ad2ba4e582a0"}, {"source": "security-advisories@github.com", "url": "https://github.com/h2o/h2o/pull/3754"}, {"source": "security-advisories@github.com", "url": "https://github.com/h2o/h2o/security/advisories/GHSA-q342-qp8v-p44c"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Received", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-770"}], "source": "security-advisories@github.com", "type": "Primary"}]}

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