{"id":"CVE-2026-100664","revision":null,"records":[{"revision":"7c01a6cdc4014f82a97a7cf3f8389825","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-100664","aliases":[],"title":"Netty 4.2.2 through 4.2.17 HTTP/1 Host Header Authority Confusion","description":"Netty's HTTP/3 codec (io.netty:netty-codec-http3) versions 4.2.2.Final through 4.2.17.Final builds the HTTP/3 :authority pseudo-header from the HTTP/1 Host header before considering the authority of an absolute-form HTTP/1 request-target. In HttpConversionUtil.toHttp3Headers(HttpMessage, boolean) — reached via Http3FrameToHttpObjectCodec(false) — a non-empty Host header takes precedence over the request-target authority, contrary to the HTTP/1.1 rule that a server receiving an absolute-form request-target must ignore the Host header. In a Netty-based HTTP/1-to-HTTP/3 gateway, proxy, or protocol bridge, a remote client can send a request such as \"GET https://trusted.example/admin HTTP/1.1\" with \"Host: attacker.example\", causing components that validate, authorize, or route on the RFC-defined request-target authority to reach a different decision than the upstream HTTP/3 peer, which receives :authority derived from the conflicting Host header. This authority confusion can affect virtual-host routing, allow-list checks, backend selection, cache keys, and URL generation. The advisory reports integrity impact only (no code execution, memory corruption, or availability impact). Fixed in 4.2.18.Final.","state":0,"publishedAt":"2026-09-26T13:23:30.478+00:00","modifiedAt":"2026-09-28T16:47:05.471+00:00","affected":[{"ecosystem":"Vendor product","name":"netty","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"netty\",\n                    \"product\": \"netty\",\n                    \"defaultStatus\": \"unaffected\",\n                    \"packageURL\": \"pkg:maven/io.netty/netty-codec-http3\",\n                    \"versions\": [\n                        {\n                            \"version\": \"4.2.2.Final\",\n                            \"status\": \"affected\",\n                            \"versionType\": \"custom\",\n                            \"lessThan\": \"4.2.18.Final\"\n                        },\n                        {\n                            \"version\": \"4.2.18.Final\",\n                            \"status\": \"unaffected\",\n                            \"versionType\": \"custom\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","score":8.7,"severity":"HIGH"},{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":7.5,"severity":"HIGH"}],"references":["https://github.com/netty/netty/security/advisories/GHSA-hfr2-x62w-v49h","https://www.vulncheck.com/advisories/netty-4.2.2-through-4.2.15-http-1-host-header-authority-confusion"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-100664","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-100664","identifiers":["CVE-2026-100664"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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Not a global EPSS backfill.","generation":"2026-11-12T08:55:39.4193399+00:00","complete":true,"records":1097,"lastAttemptAt":"2026-11-12T08:55:39.4193399+00:00","lastSuccessAt":"2026-11-12T08:55:39.5676932+00:00","error":null,"lastVerifiedAt":"2026-11-12T08:55:39.5676956+00:00","snapshotPublishedAt":null,"importing":false,"stagedRecords":0,"checkedIdentifiers":null,"expectedIdentifiers":null,"failedIdentifiers":null},{"source":"nvd","scope":"Rolling NVD lookups of CVE aliases in current public OSV archives; 500 identifiers per refresh, rechecked after 48 hours. Not a global NVD catalog. Successful not-found lookups count as checked; they do not imply withdrawal or safety. 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