{"id":"CVE-2026-100662","summary":"Netty HTTP/3 QPACK encoder-stream unbounded memory exhaustion DoS","details":"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.","aliases":["GHSA-f64r-x647-cg8w"],"modified":"2026-09-28T03:48:30.767601822Z","published":"2026-09-26T13:23:28.990Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100662.json","cna_assigner":"VulnCheck","cwe_ids":["CWE-400"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100662.json"},{"type":"ADVISORY","url":"https://github.com/netty/netty/security/advisories/GHSA-f64r-x647-cg8w"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-100662"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/netty-http-3-qpack-encoder-stream-unbounded-memory-exhaustion-dos"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/netty/netty","events":[{"introduced":"09e64d259c99be8b5b2a471a78f11e65eb82598a"},{"fixed":"2521f494432e27415a567d3a81a9eb907abf20b3"}],"database_specific":{"extracted_events":[{"introduced":"4.2.0.Final"},{"fixed":"4.2.18.Final"},{"fixed":"4.2.17.Final"}],"source":["AFFECTED_FIELD","DESCRIPTION"]}}],"versions":["netty-clang-bin","netty-4.2.17.Final","netty-4.2.16.Final","netty-4.2.15.Final","netty-4.2.14.Final","netty-4.2.13.Final","netty-4.2.12.Final","netty-4.2.11.Final","netty-4.2.10.Final","netty-4.2.9.Final","netty-4.2.8.Final","netty-4.2.7.Final","netty-4.2.6.Final","netty-4.2.5.Final","netty-4.2.4.Final","netty-4.2.3.Final","netty-4.2.2.Final","netty-4.2.1.Final","netty-4.2.0.Final"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-100662.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}