{"id":"CVE-2026-100662","title":"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…","summary":"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…","severity":"high","cvss":7.5,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","cwe":["CWE-400","CWE-770"],"vendor":"netty","product":"netty","affected":["netty >= 4.2.0.Final < 4.2.18.Final"],"published":"2026-09-26","updated":"2026-09-30","sourceUpdated":"2026-09-30T15:22:15.423","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-100662","references":[{"url":"https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w","label":"disclosure@vulncheck.com"},{"url":"https://www.vulncheck.com/advisories/netty-http-3-qpack-encoder-stream-unbounded-memory-exhaustion-dos","label":"disclosure@vulncheck.com"},{"url":"https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w","label":"134c704f-9b21-4f2e-91b3-4a467353bcc0"},{"url":"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-100662.json"},{"url":"https://access.redhat.com/security/cve/CVE-2026-100662"},{"url":"https://bugzilla.redhat.com/show_bug.cgi?id=2541871"},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-100662"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-100662"}],"tags":["nvd","cve.org","exploit-available","csaf","vex","red-hat"],"exploitAvailable":true,"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"partial","timestamp":"2026-09-30T14:53:08.105333Z"},"epss":0.00416,"epssPercentile":0.35684,"ingestedAt":"2026-09-26T13:33:20.916Z","slug":"CVE-2026-100662","body":"## Overview\n\nNetty'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.\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.\n\n## Vendor advisories\n\n- **Red Hat VEX** · Important · affected: Red Hat OpenShift Dev Spaces · no fix planned: Red Hat OpenShift Dev Spaces · updated 2026-09-29 · [vex](https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-100662.json)","depth":"midnight","depthScore":53,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[{"seq":213720,"id":"CVE-2026-100662","ts":1790780947369,"field":"exploit_available","old":"false","new":"true"}]}