CVE-2026-26963: Cilium may not enforce host firewall policies when Native Routing, WireGuard and Node Encryption are enabled

Severity: medium (CVSS 5.4 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-02-20 · updated 2026-06-17
Weakness: CWE-863

Description

Cilium is a networking, observability, and security solution with an eBPF-based dataplane. Versions 1.18.0 through 1.18.5 will incorrectly permit traffic from Pods on other nodes when Native Routing, WireGuard and Node Encryption are enabled. This issue has been fixed in version 1.18.6.

Affected products

cilium: from 1.18.0 before 1.18.6 — fixed in 1.18.6

How to fix

Upgrade to a fixed version: cilium 1.18.6. Check the vendor advisory for mitigations.

References

https://github.com/cilium/cilium/commit/88e28e1e62c0b1a02c3f0fc22d888ac9eefbe885
https://github.com/cilium/cilium/pull/42892
https://github.com/cilium/cilium/releases/tag/v1.18.6
https://github.com/cilium/cilium/security/advisories/GHSA-5r23-prx4-mqg3

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