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CiliumApplication

CVE-2026-56743

MEDIUM · 5.4 CVSS v3.1 Published 2026-07-15
Fix available
A fix is available. Upgrade to 1.19.5 or later.
See remediation →
56/100
Remediation priority · Elevated
Zero-click 5 weeks old

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Cilium 1.19.0-1.19.4, when using Kubernetes NetworkPolicy with CIDR-based ipBlock rules that lack pod or namespace selectors, and Cilium is configured with a custom clusterName (not the default 'any'), the parser erroneously instantiates a wildcard namespace allow rule. This incorrectly permits traffic from other workloads in the same namespace as the policy subject, bypassing intended CIDR restrictions.

MitigationUpgrade Cilium to version 1.19.5 or later to resolve the parsing logic error that allows unintended traffic from same-namespace workloads.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
CiliumApplication
Affected:>= 1.19.0, < 1.19.5

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Adjacent
Complexity
Low
Privileges
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

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

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Check Cilium version
    Run 'cilium version' or inspect the Cilium agent DaemonSet image tag to determine the installed version
    Affected if The version is 1.19.0, 1.19.1, 1.19.2, 1.19.3, or 1.19.4 (anything >=1.19.0 and <1.19.5)
  2. Identify NetworkPolicies with CIDR ipBlock rules
    Run 'kubectl get networkpolicies -o yaml' and search for policies containing 'ipBlock' with a 'cidr' field
    Affected if Any NetworkPolicy exists that uses ipBlock with a CIDR range
  3. Check if affected NetworkPolicies lack pod or namespace selectors
    Examine the NetworkPolicy spec - verify that there is no 'podSelector' and no 'namespaceSelector' defined in the policy
    Affected if The NetworkPolicy has no podSelector and no namespaceSelector in its spec
  4. Verify custom clusterName configuration
    Check the Cilium ConfigMap (kubectl get cm -n kube-system cilium-config) or Helm values for the 'clusterName' setting
    Affected if clusterName is set to any value other than 'any' or the default

If all four conditions are true (affected Cilium version, CIDR-based ipBlock NetworkPolicy exists, that policy lacks selectors, and clusterName is custom), the environment is vulnerable to bypassed CIDR restrictions allowing same-namespace traffic.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 1.19.5 or later
Fixed in 1.19.5
Interim mitigation

Upgrade Cilium to version 1.19.5 or later to resolve the parsing logic error that allows unintended traffic from same-namespace workloads.

Recommended fix High confidence

1.19.5

  1. Identify all Cilium control plane and worker nodes in the cluster
  2. Upgrade Cilium to version 1.19.5 on all control plane nodes following standard upgrade procedures
  3. Restart or upgrade the Cilium agent on all worker nodes
  4. Verify that NetworkPolicy specifications with CIDR-based ipBlock rules (without pod or namespace selectors) now correctly enforce the intended policy and do not generate wildcard namespace allow rules
  5. Confirm the clusterName configuration is working as expected with the upgrade

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Cilium Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing4.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,080
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,328.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-56743 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data