CVE-2026-56746: Netty Security Control Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6cqp-g7gg-8hr5",
  "modified" : "2026-07-22T21:42:17Z",
  "published" : "2026-07-22T21:42:17Z",
  "aliases" : [ "CVE-2026-56746" ],
  "summary" : "Netty: Security Control Bypass via CORS Short-Circuit Failure",
  "details" : "### Summary\nNetty's CorsHandler provides a `shortCircuit()` configuration designed to reject unauthorized cross-origin requests immediately, acting as a security control before requests reach the application. However, due to a logical operator error in the origin evaluation process, this protection can be entirely bypassed. An attacker can bypass the short-circuit mechanism by sending a request with an `Origin: null` header. This failure forwards unauthorized requests to the backend application, bypassing intended access controls.\n\n### Details\nIn `io.netty.handler.codec.http.cors.CorsHandler#channelRead`, the short-circuit logic relies on the configuration returned by `getForOrigin(origin)` to determine if an origin is authorized. If `getForOrigin` returns a configuration object, the short-circuit check `(!(origin == null || config != null))` is bypassed, and the request proceeds to the backend.\n\nThe vulnerability is located in the `getForOrigin` method:\n\n```java\n            if (corsConfig.isNullOriginAllowed() || NULL_ORIGIN.equals(requestOrigin)) {\n                return corsConfig;\n            }\n```\n\nIf an attacker sends `Origin: null`, `NULL_ORIGIN.equals(requestOrigin)` evaluates to true. The method returns the configuration object regardless of whether `isNullOriginAllowed()` was configured by the developer. The short-circuit is bypassed.\n\n### Impact\nApplications relying on CorsHandler's short-circuit feature to prevent unauthorized cross-origin requests from reaching their backend logic are completely exposed. The framework fails to enforce the developer's intended access controls, allowing unauthorized requests to be processed.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.netty:netty-codec-http"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.2.0.Final"
      }, {
        "fixed" : "4.2.16.Final"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.netty:netty-codec-http"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.1.136.Final"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/security/advisories/GHSA-6cqp-g7gg-8hr5"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-56746"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/netty/netty"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/releases/tag/netty-4.1.136.Final"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/releases/tag/netty-4.2.16.Final"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-07-22T21:42:17Z",
    "nvd_published_at" : "2026-07-21T22:17:14Z"
  }
}