Vulnerability-Lookup

GHSA-FM8W-2M5W-9J7R

Vulnerability from github – Published: 2026-09-03 17:17 – Updated: 2026-09-03 17:17

Summary

Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match

Details

Impact

Standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule under specific cluster configurations.

When Cilium deployment is configured with a specific custom clusterName (rather than the default "any" value), the parser incorrectly instantiates a pod selector on selectorless peer definitions. This leads to Cilium appending an unintended wildcard namespace label selector to the policy's allowed Layer 3 rules, which allows traffic from other workloads in the same namespace as the subject of the policy.

Example policy affected by this issue:

apiVersion: networking.k8s.io/v1
kind: NetworkPolicy
metadata:
  name: test-server
  namespace: default
spec:
  podSelector:
    matchLabels:
      app: test-server
  policyTypes:
  - Ingress
  ingress:
  - from:
    - ipBlock:
        cidr: 192.0.2.3

In affected versions, this policy erroneously allows the test-server Pod in the default namespace to receive any traffic from other workloads running in the default namespace.

Patches

This issue has been patched in:

Cilium v1.19.5

Releases below v1.19.0 are not affected.

This issue affects:

Cilium v1.19 between v1.19.0 and v1.19.4 inclusive

Workarounds

Developers can create the equivalent policy using CiliumNetworkPolicy fromCIDR expressions. CiliumNetworkPolicy and CiliumClusterwideNetworkPolicy are not affected by this issue.

Acknowledgements

Special thanks to @TheBeeZee for reporting this issue and preparing the fix, and to @fristonio and @odinuge for their assistance in reviewing the solution.

For more information

If a vulnerability affecting Cilium appears to have been found, the Cilium security team strongly encourages reporting it to the security mailing list at security@cilium.io. This is a private mailing list for the Cilium security team, and the report will be treated as top priority.

Severity

5.4 (Medium)


                  
                    CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

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JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cilium/cilium"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.19.0"
            },
            {
              "fixed": "1.19.5"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-56743"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-03T17:17:47Z",
    "nvd_published_at": "2026-07-15T20:17:51Z",
    "severity": "MODERATE"
  },
  "details": "### Impact\n\nStandard Kubernetes `NetworkPolicy` specifications using CIDR-based `ipBlock` rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule under specific cluster configurations.\n\nWhen Cilium deployment is configured with a specific custom `clusterName` (rather than the default `\"any\"` value), the parser incorrectly instantiates a pod selector on selectorless peer definitions. This leads to Cilium appending an unintended wildcard namespace label selector to the policy\u0027s allowed Layer 3 rules, which allows traffic from other workloads in the same namespace as the subject of the policy.\n\nExample policy affected by this issue:\n```\napiVersion: networking.k8s.io/v1\nkind: NetworkPolicy\nmetadata:\n  name: test-server\n  namespace: default\nspec:\n  podSelector:\n    matchLabels:\n      app: test-server\n  policyTypes:\n  - Ingress\n  ingress:\n  - from:\n    - ipBlock:\n        cidr: 192.0.2.3\n```\n\nIn affected versions, this policy erroneously allows the `test-server` Pod in the `default` namespace to receive any traffic from other workloads running in the `default` namespace.\n\n### Patches\n\nThis issue has been patched in:\n\n- Cilium v1.19.5\n\nReleases below v1.19.0 are not affected.\n\n### This issue affects:\n\n- Cilium v1.19 between v1.19.0 and v1.19.4 inclusive\n\n### Workarounds\n\nDevelopers can create the equivalent policy using CiliumNetworkPolicy [fromCIDR expressions](https://docs.cilium.io/en/stable/security/policy/layer3/#ip-cidr-based). CiliumNetworkPolicy and CiliumClusterwideNetworkPolicy are not affected by this issue.\n\n### Acknowledgements\n\nSpecial thanks to @TheBeeZee for reporting this issue and preparing the fix, and to @fristonio and @odinuge for their assistance in reviewing the solution.\n\n### For more information\n\nIf a vulnerability affecting Cilium appears to have been found, the Cilium security team strongly encourages reporting it to the security mailing list at security@cilium.io. This is a private mailing list for the Cilium security team, and the report will be treated as top priority.",
  "id": "GHSA-fm8w-2m5w-9j7r",
  "modified": "2026-09-03T17:17:47Z",
  "published": "2026-09-03T17:17:47Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cilium/cilium/security/advisories/GHSA-fm8w-2m5w-9j7r"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-56743"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cilium/cilium/pull/46305"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cilium/cilium/pull/46456"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cilium/cilium/commit/1c84ae3b58a7cd54f7ee355e6c524c82f620eae8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cilium/cilium/commit/bacea640404c0805c23515353dc1681c5bf35171"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cilium/cilium"
    },
    {
      "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:L/UI:N/S:C/C:L/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match"
}

CVE-2026-56743 (GCVE-0-2026-56743)

Vulnerability from cvelistv5 – Published: 2026-07-15 19:15 – Updated: 2026-07-16 13:03

Title

Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match

Summary

Cilium is a networking, observability, and security solution. From 1.19.0 to 1.19.4, standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule when Cilium is configured with a custom clusterName rather than the default any value. The parser incorrectly instantiates a pod selector on selectorless peer definitions, allowing traffic from other workloads in the same namespace as the subject of the policy. This issue is fixed in version 1.19.5.

Severity

5.4 (Medium)


                        
                          CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-07-16 13:02 UTC

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M mitre root

References

6 references

URL	Tags
https://github.com/cilium/cilium/security/advisor…	x_refsource_CONFIRM
https://github.com/cilium/cilium/pull/46305	x_refsource_MISC
https://github.com/cilium/cilium/pull/46456	x_refsource_MISC
https://github.com/cilium/cilium/commit/1c84ae3b5…	x_refsource_MISC
https://github.com/cilium/cilium/commit/bacea6404…	x_refsource_MISC
https://github.com/cilium/cilium/releases/tag/v1.19.5	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
cilium	cilium	Affected: >= 1.19.0, < 1.19.5

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-56743",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-16T13:02:42.889041Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
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        "providerMetadata": {
          "dateUpdated": "2026-07-16T13:03:36.080Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
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      }
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    "cna": {
      "affected": [
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          "product": "cilium",
          "vendor": "cilium",
          "versions": [
            {
              "status": "affected",
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            }
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        }
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      "descriptions": [
        {
          "lang": "en",
          "value": "Cilium is a networking, observability, and security solution. From 1.19.0 to 1.19.4, standard Kubernetes NetworkPolicy specifications using CIDR-based ipBlock rules without pod or namespace selectors erroneously generate a wildcard namespace allow rule when Cilium is configured with a custom clusterName rather than the default any value. The parser incorrectly instantiates a pod selector on selectorless peer definitions, allowing traffic from other workloads in the same namespace as the subject of the policy. This issue is fixed in version 1.19.5."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "ADJACENT_NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.4,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "LOW",
            "integrityImpact": "LOW",
            "privilegesRequired": "LOW",
            "scope": "CHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-863",
              "description": "CWE-863: Incorrect Authorization",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-15T19:15:30.924Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/cilium/cilium/security/advisories/GHSA-fm8w-2m5w-9j7r",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/cilium/cilium/security/advisories/GHSA-fm8w-2m5w-9j7r"
        },
        {
          "name": "https://github.com/cilium/cilium/pull/46305",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cilium/cilium/pull/46305"
        },
        {
          "name": "https://github.com/cilium/cilium/pull/46456",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cilium/cilium/pull/46456"
        },
        {
          "name": "https://github.com/cilium/cilium/commit/1c84ae3b58a7cd54f7ee355e6c524c82f620eae8",
          "tags": [
            "x_refsource_MISC"
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          "url": "https://github.com/cilium/cilium/commit/1c84ae3b58a7cd54f7ee355e6c524c82f620eae8"
        },
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          "name": "https://github.com/cilium/cilium/commit/bacea640404c0805c23515353dc1681c5bf35171",
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          "url": "https://github.com/cilium/cilium/commit/bacea640404c0805c23515353dc1681c5bf35171"
        },
        {
          "name": "https://github.com/cilium/cilium/releases/tag/v1.19.5",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/cilium/cilium/releases/tag/v1.19.5"
        }
      ],
      "source": {
        "advisory": "GHSA-fm8w-2m5w-9j7r",
        "discovery": "UNKNOWN"
      },
      "title": "Cilium may unexpectedly allow ingress traffic from the local namespace when a Kubernetes NetworkPolicy is configured with an ipBlock match"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-56743",
    "datePublished": "2026-07-15T19:15:30.924Z",
    "dateReserved": "2026-06-22T19:17:28.959Z",
    "dateUpdated": "2026-07-16T13:03:36.080Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.