GHSA-W7C2-W76W-5HMJ

Vulnerability from github – Published: 2026-09-24 19:38 – Updated: 2026-09-24 19:38
VLAI
Summary
Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces
Details

Impact

In Cilium clusters using 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.

Gateway API functionality is disabled by default.

Patches

This issue affects:

  • Cilium v1.19 from v1.19.0 to v1.19.4 inclusive
  • Cilium v1.18 from v1.18.0 to v1.18.10 inclusive
  • All versions of Cilium before v1.17.17

This issue is patched in:

  • Cilium v1.19.5
  • Cilium v1.18.11
  • Cilium v1.17.17

Workarounds

There 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.

Acknowledgements

The 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.

For more information

If you have any questions or comments about this advisory, please reach out on Slack.

If 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. This is a private mailing list for the Cilium security team, and your report will be treated as top priority.

Severity
5.9 (Medium)
CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L
Show details on source website
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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cilium/cilium"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.17.17"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cilium/ciliumCilium"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.18.0"
            },
            {
              "fixed": "1.18.11"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cilium/cilium"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.19.0"
            },
            {
              "fixed": "1.19.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-56742"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-862"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-24T19:38:39Z",
    "nvd_published_at": "2026-07-15T20:17:51Z",
    "severity": "MODERATE"
  },
  "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.",
  "id": "GHSA-w7c2-w76w-5hmj",
  "modified": "2026-09-24T19:38:39Z",
  "published": "2026-09-24T19:38:39Z",
  "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"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:A/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:L",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces"
}



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  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.



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