{"id":"CVE-2026-100662","state":"PUBLISHED","title":"Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS","description":"Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final contain an uncontrolled resource consumption vulnerability in the QPACK encoder-stream instruction decoder (QpackEncoderHandler, installed on the peer-initiated unidirectional QPACK encoder stream, type 0x02). The handler accepts an attacker-declared string-literal length of up to Integer.MAX_VALUE (~2 GiB) for the Name Length and Value Length fields of the \"Insert With Literal Name\" instruction (RFC 9204 §4.3.3), with no per-instruction or per-literal length cap and no cumulation-size limit; the existing HTTP/3 limits (maxHeaderListSize, maxUnknownFramePayloadLength, DEFAULT_MAX_FIELD_SECTION_SIZE) are not applied to this handler. A remote, unauthenticated peer with an established HTTP/3 connection to a default Netty HTTP/3 server can declare a very large literal length and then trickle fewer bytes than declared, causing the ByteToMessageDecoder MERGE cumulator to retain and grow the per-connection buffer, and ultimately triggering a large byte-array allocation. This leads to unbounded per-connection heap growth and OutOfMemoryError, resulting in denial of service. Fixed in 4.2.18.Final.","publishedAt":"2026-09-26T13:23:28.990Z","updatedAt":"2026-09-30T14:53:30.335Z","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":["netty netty"],"affected":[{"vendor":"netty","product":"netty","packageURL":"pkg:maven/io.netty/netty-codec-http3","defaultStatus":"unaffected","versions":[{"version":"4.2.0.Final","status":"affected","lessThan":"4.2.18.Final","versionType":"custom"},{"version":"4.2.18.Final","status":"unaffected","versionType":"custom"}]}],"references":["https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w","https://www.vulncheck.com/advisories/netty-http-3-qpack-encoder-stream-unbounded-memory-exhaustion-dos"],"weaknesses":["CWE-400"],"ingestedAt":"2026-10-29T20:10:13.529Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/100xxx/CVE-2026-100662.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-100662","state":"PUBLISHED","datePublished":"2026-09-26T13:23:28.990Z","dateUpdated":"2026-09-30T14:53:30.335Z","assignerShortName":"VulnCheck","assignerOrgId":"83251b91-4cc7-4094-a5c7-464a1b83ea10","dateReserved":"2026-09-26T02:33:59.039Z"},"containers":{"cna":{"title":"Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS","descriptions":[{"lang":"en","value":"Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.0.Final through 4.2.17.Final contain an uncontrolled resource consumption vulnerability in the QPACK encoder-stream instruction decoder (QpackEncoderHandler, installed on the peer-initiated unidirectional QPACK encoder stream, type 0x02). The handler accepts an attacker-declared string-literal length of up to Integer.MAX_VALUE (~2 GiB) for the Name Length and Value Length fields of the \"Insert With Literal Name\" instruction (RFC 9204 §4.3.3), with no per-instruction or per-literal length cap and no cumulation-size limit; the existing HTTP/3 limits (maxHeaderListSize, maxUnknownFramePayloadLength, DEFAULT_MAX_FIELD_SECTION_SIZE) are not applied to this handler. A remote, unauthenticated peer with an established HTTP/3 connection to a default Netty HTTP/3 server can declare a very large literal length and then trickle fewer bytes than declared, causing the ByteToMessageDecoder MERGE cumulator to retain and grow the per-connection buffer, and ultimately triggering a large byte-array allocation. This leads to unbounded per-connection heap growth and OutOfMemoryError, resulting in denial of service. Fixed in 4.2.18.Final."}],"affected":[{"vendor":"netty","product":"netty","packageURL":"pkg:maven/io.netty/netty-codec-http3","defaultStatus":"unaffected","versions":[{"version":"4.2.0.Final","status":"affected","lessThan":"4.2.18.Final","versionType":"custom"},{"version":"4.2.18.Final","status":"unaffected","versionType":"custom"}]}],"references":[{"url":"https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w","tags":["vendor-advisory"],"name":"GitHub Security Advisory (GHSA-f64r-x647-cg8w)"},{"url":"https://www.vulncheck.com/advisories/netty-http-3-qpack-encoder-stream-unbounded-memory-exhaustion-dos","name":"VulnCheck Advisory: Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS","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":"2026-09-27T16:27:48.157Z"},"datePublic":"2026-09-10T00:00:00.000Z","cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:netty:netty:*:*:*:*:*:*:*:*","versionStartIncluding":"4.2.0.final","versionEndExcluding":"4.2.18.final"}]}]}],"credits":[{"lang":"en","value":"manus-use","type":"reporter"}],"x_generator":{"engine":"vulncheck-endgame"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-09-30T14:53:08.105333Z","id":"CVE-2026-100662","options":[{"Exploitation":"poc"},{"Automatable":"yes"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-09-30T14:53:30.335Z"}}]}}}