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Cilium: Namespaced HTTPRoutes can redirect traffic to other namespaces

Type: advisorySource: OSV1 source record

### Impact In 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. 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](https://docs.cilium.io/en/latest/community/community/). 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](mailto:security@cilium.io). This is a private mailing list for the Cilium security team, and your report w

Announced Source revision 1
Original source ↗

GHSA-w7c2-w76w-5hmj

Primary source · Revision 1

Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.

Security context

Source reference: osv:GHSA-w7c2-w76w-5hmj

github.com/cilium/cilium

Source reference: /affected/0/package/name

Affected versions
Not stated in this record
Fixed versions
1.17.17

Source reference: /affected/0/ranges

Prerequisites
Not stated in this record

github.com/cilium/ciliumCilium

Source reference: /affected/1/package/name

Affected versions
Not stated in this record
Fixed versions
1.18.11

Source reference: /affected/1/ranges

Prerequisites
Not stated in this record

github.com/cilium/cilium

Source reference: /affected/2/package/name

Affected versions
Not stated in this record
Fixed versions
1.19.5

Source reference: /affected/2/ranges

Prerequisites
Not stated in this record

Structured affected-version data

Original package identities and version rules from this source.

[
  {
    "ranges": [
      {
        "type": "SEMVER",
        "events": [
          {
            "introduced": "0"
          },
          {
            "fixed": "1.17.17"
          }
        ]
      }
    ],
    "package": {
      "name": "github.com/cilium/cilium",
      "purl": "pkg:golang/github.com/cilium/cilium",
      "ecosystem": "Go"
    },
    "database_specific": {
      "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-w7c2-w76w-5hmj/GHSA-w7c2-w76w-5hmj.json"
    }
  },
  {
    "ranges": [
      {
        "type": "SEMVER",
        "events": [
          {
            "introduced": "1.18.0"
          },
          {
            "fixed": "1.18.11"
          }
        ]
      }
    ],
    "package": {
      "name": "github.com/cilium/ciliumCilium",
      "purl": "pkg:golang/github.com/cilium/ciliumCilium",
      "ecosystem": "Go"
    },
    "database_specific": {
      "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-w7c2-w76w-5hmj/GHSA-w7c2-w76w-5hmj.json"
    }
  },
  {
    "ranges": [
      {
        "type": "SEMVER",
        "events": [
          {
            "introduced": "1.19.0"
          },
          {
            "fixed": "1.19.5"
          }
        ]
      }
    ],
    "package": {
      "name": "github.com/cilium/cilium",
      "purl": "pkg:golang/github.com/cilium/cilium",
      "ecosystem": "Go"
    },
    "database_specific": {
      "source": "https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/09/GHSA-w7c2-w76w-5hmj/GHSA-w7c2-w76w-5hmj.json"
    }
  }
]
Related CVEs
CVE-2026-56742

Source reference: /aliases

Publisher severity

No explicit severity was provided.

Linked CVE context

These ratings describe the referenced vulnerabilities and products. They are not a severity rating for every application using this dependency.

CVE-2026-56742 · High

cilium

CVE-2026-56742 · High

cilium-operator

CVE-2026-56742 · High

hubble-relay

Event
#63967 · Revision 1
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