CVE-2026-28898: SwiftNIO HTTP/2 HTTP/2-to-HTTP/1 Request Smuggling Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-4px2-pw77-vc85",
  "modified" : "2026-07-15T21:23:10Z",
  "published" : "2026-06-12T15:08:16Z",
  "aliases" : [ "CVE-2026-28898" ],
  "summary" : "SwiftNIO HTTP/2: HTTP/2-to-HTTP/1 Request Smuggling via unvalidated :path pseudo-header in HTTP2ToHTTP1Codec",
  "details" : "swift-nio-http2's HTTP/2-to-HTTP/1.1 codec (`HTTP2FramePayloadToHTTP1ServerCodec` / `HTTP2ToHTTP1ServerCodec`) did not validate pseudo-header values for control characters before placing them into the translated HTTP/1.1 message. A remote attacker could send an HTTP/2 request containing CR (\\r), LF (\\n), or NUL (\\0) bytes in pseudo-header values such as `:path`, and when the server translated this to HTTP/1.1 — for example in a reverse-proxy configuration — the resulting output could contain injected headers or entirely smuggled requests.\n\nThis is an HTTP/2-to-HTTP/1.1 request smuggling vulnerability. HTTP/2's binary framing means that CRLF bytes are never parsed as line terminators at the HTTP/2 layer, so they pass through transparently to the HTTP/1.1 output. Any swift-nio-http2 server that translates HTTP/2 requests to HTTP/1.1 and forwards them to a backend is affected. Server-side Swift frameworks such as Vapor that use this codec in a reverse-proxy pattern are directly affected.\n\nThis vulnerability is related to https://github.com/advisories/GHSA-7fj7-39wj-c64f in swift-nio, which addressed CRLF injection in HTTP/1.1 header values but did not cover pseudo-header values in the HTTP/2 layer.\n\nThis vulnerability is also related to https://github.com/advisories/GHSA-cq87-8r7h-962v in swift-nio, which addressed CRLF injection in HTTP/1.1 version, method and path.\n\nswift-nio-http2 1.44.0 adds validation of all pseudo-header values (:path, :authority, :scheme, :method, and :status) at both the HPACK header validation layer and the HTTP/2-to-HTTP/1.1 translation layer. Requests or responses containing CR, LF, or NUL bytes in any pseudo-header value are now rejected with a connection error.\n\nSwiftNIO recommends all adopters upgrade to 1.44.0 as soon as possible.\n\nSwiftNIO thanks @kuranikaran for filing this issue and the support in fixing it.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "SwiftURL",
      "name" : "github.com/apple/swift-nio-http2"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.44.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/apple/swift-nio-http2/security/advisories/GHSA-4px2-pw77-vc85"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-28898"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/apple/swift-nio-http2/commit/61d1b44f6e4e118792be1cff88ee2bc0267c6f9a"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/apple/swift-nio-http2"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-116", "CWE-444" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-06-12T15:08:16Z",
    "nvd_published_at" : "2026-06-25T19:16:36Z"
  }
}