CVE-2026-56742: Cilium Namespaced HTTPRoutes Can Redirect Traffic Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-w7c2-w76w-5hmj",
  "modified" : "2026-09-24T19:38:39Z",
  "published" : "2026-09-24T19:38:39Z",
  "aliases" : [ "CVE-2026-56742" ],
  "summary" : "Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces",
  "details" : "### Impact\n\nIn Cilium clusters using [Gateway API](https://docs.cilium.io/en/stable/network/servicemesh/gateway-api/gateway-api/), users with permissions to create or update namespaced HTTPRoutes can mirror HTTP traffic to any Service in any namespace, bypassing the ReferenceGrant authorization mechanism.\n\nGateway API functionality is disabled by default.\n\n### Patches\n\nThis issue affects:\n\n* Cilium v1.19 from v1.19.0 to v1.19.4 inclusive\n* Cilium v1.18 from v1.18.0 to v1.18.10 inclusive\n* All versions of Cilium before v1.17.17\n\nThis issue is patched in:\n\n* Cilium v1.19.5\n* Cilium v1.18.11\n* Cilium v1.17.17\n\n### Workarounds\n\nThere is no workaround to this issue. Users of this feature who are unable to upgrade can mitigate the risk by ensuring that RBAC permissions to create `HTTPRoute` objects are only granted to cluster admins.\n\n### Acknowledgements\n\nThe Cilium community has worked together with members of Isovalent to prepare these mitigations. Special thanks to @galanko for reporting the issue and @mhofstetter for their work on triaging and remediating this issue.\n\n### For more information\n\nIf you have any questions or comments about this advisory, please reach out on [Slack](https://docs.cilium.io/en/latest/community/community/).\n\nIf you think you have found a vulnerability affecting Cilium, we strongly encourage you to report it to our security mailing list at [security@cilium.io](mailto:security@cilium.io). This is a private mailing list for the Cilium security team, and your report will be treated as top priority.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cilium/cilium"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "1.17.17"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cilium/ciliumCilium"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.18.0"
      }, {
        "fixed" : "1.18.11"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Go",
      "name" : "github.com/cilium/cilium"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "1.19.0"
      }, {
        "fixed" : "1.19.5"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/security/advisories/GHSA-w7c2-w76w-5hmj"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-56742"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/commit/7422068aff67ac77c7dcc57aa5b9240c91333deb"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/commit/e0b1cef513ff910323f3743e9f3e3d86721e4857"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/commit/f23929cff682d6ed0dc158070812cb302fc0032b"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/commit/fd47963ea394d5e8fa4a88c40a79063430c512ca"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/cilium/cilium"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/releases/tag/v1.17.17"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/releases/tag/v1.18.11"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/cilium/cilium/releases/tag/v1.19.5"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-862" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-09-24T19:38:39Z",
    "nvd_published_at" : "2026-07-15T20:17:51Z"
  }
}