{"id":"CVE-2026-100664","summary":"Netty 4.2.2 through 4.2.17 HTTP/1 Host Header Authority Confusion","details":"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.","aliases":["GHSA-hfr2-x62w-v49h"],"modified":"2026-09-30T03:30:55.191189692Z","published":"2026-09-26T13:23:30.478Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100664.json","cna_assigner":"VulnCheck","cwe_ids":["CWE-20"]},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/100xxx/CVE-2026-100664.json"},{"type":"ADVISORY","url":"https://github.com/netty/netty/security/advisories/GHSA-hfr2-x62w-v49h"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-100664"},{"type":"ADVISORY","url":"https://www.vulncheck.com/advisories/netty-4.2.2-through-4.2.15-http-1-host-header-authority-confusion"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/netty/netty","events":[{"introduced":"660edeaefad4a4cedbd61584e8f668ad2d89f0b8"},{"fixed":"2521f494432e27415a567d3a81a9eb907abf20b3"}],"database_specific":{"extracted_events":[{"introduced":"4.2.2.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"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-100664.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:H/VA:N/SC:N/SI:N/SA:N"}]}