Authorization Flaw in github.com/cilium/cilium (CVE-2026-56743)
Summary
Vulnerability in github.com/cilium/cilium (CVE-2026-56743). Risk of unauthorized operations or information disclosure. Exploitable via NetworkPolicy. Mitigation: upgrade to 1.19.5 or later.
Original description
The description as published by the source.
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.
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-56743 has been found in github.com/cilium/cilium.
Attackers can target a specific entry point like NetworkPolicy over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.4/10.
What to do: upgrade github.com/cilium/cilium to 1.19.5 or later.
If unsure, ask your IT team or search "github.com/cilium/cilium CVE-2026-56743" on the vendor's site.
CVE-2026-56743 (github.com/cilium/cilium) — CWE-863 / CVSS v3 5.4
Attack vector: adjacent-network / no user interaction
Attack surface: NetworkPolicy / ipBlock / clusterName / default
Patched: 1.19.5 — apply immediately
Workaround: Developers can create the equivalent policy using CiliumNetworkPolicy fromCIDR expressions.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Incorrect authorization (CWE-863) exists in github.com/cilium/cilium. Attackers reach the vulnerable code path via NetworkPolicy.
Check the vendor advisory for the affected versions of github.com/cilium/cilium. Attack surface: NetworkPolicy / ipBlock / clusterName / default.
Severity: Medium (CVSS 5.4/10). Risk of unauthorized operations or information disclosure.
Update to 1.19.5.
Workaround: Developers can create the equivalent policy using CiliumNetworkPolicy fromCIDR expressions.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/cilium/cilium' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'github.com/cilium/cilium' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
github.com/cilium/ciliumを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Developers can create the equivalent policy using CiliumNetworkPolicy [fromCIDR expressions](https://docs.cilium.io/en/stable/security/policy/layer3/#ip-cidr-based).パッチが適用されるまでの応急処置として、Developers can create the equivalent policy using CiliumNetworkPolicy fromCIDR expressions. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade github.com/cilium/cilium to 1.19.5ステージング環境で 1.19.5 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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4Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory github.com
- patch github.com
- patch github.com
- patch github.com
- patch github.com
- web github.com
- web nvd.nist.gov
- web github.com