CVE-2026-56743: cilium Auth Bypass — Fix

Description

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.

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CVSS v3.1 Score

5.4

MEDIUM

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

EPSS — Exploit Prediction

0.0016

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-863 Incorrect Authorization

Affected Products

Vendor	Product	Versions
cilium	cilium	1.19.0 — 1.19.5

References

Advisories & Patches

https://github.com/cilium/cilium/commit/1c84ae3b58a7cd54f7ee355e6c524c82f620eae8 https://github.com/cilium/cilium/commit/bacea640404c0805c23515353dc1681c5bf35171 https://github.com/cilium/cilium/pull/46305 https://github.com/cilium/cilium/pull/46456 https://github.com/cilium/cilium/security/advisories/GHSA-fm8w-2m5w-9j7r

Other References

https://github.com/cilium/cilium/releases/tag/v1.19.5

Frequently Asked Questions

What is CVE-2026-56743? +

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. It has a CVSS v3.1 base score of 5.4 (MEDIUM).

How severe is CVE-2026-56743? +

CVE-2026-56743 has a CVSS v3.1 score of 5.4 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0016, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-56743? +

CVE-2026-56743 affects products from cilium, specifically: cilium. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-56743? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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