CVE-2023-27594: Cilium vulnerable to potential network policy bypass when routing IPv6 traffic

Severity: high (CVSS 7.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.6% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-03-17 · updated 2026-06-17
Weakness: CWE-285

Description

Cilium is a networking, observability, and security solution with an eBPF-based dataplane. Prior to versions 1.11.15, 1.12.8, and 1.13.1, under specific conditions, Cilium may misattribute the source IP address of traffic to a cluster, identifying external traffic as coming from the host on which Cilium is running. As a consequence, network policies for that cluster might be bypassed, depending on the specific network policies enabled. This issue only manifests when Cilium is routing IPv6 traffic and NodePorts are used to route traffic to pods. IPv6 and endpoint routes are both disabled by default. The problem has been fixed and is available on versions 1.11.15, 1.12.8, and 1.13.1. As a workaround, disable IPv6 routing.

Affected products

cilium: before 1.11.15; from 1.12.0 before 1.12.8; from 1.13.0 before 1.13.1 — fixed in 1.11.15, 1.12.8, 1.13.1

How to fix

Upgrade to a fixed version: cilium 1.11.15, 1.12.8, 1.13.1. Check the vendor advisory for mitigations.

References

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