CVE-2026-66785: Submariner: submariner: missing validation of remote endpoint subnets and clusterid enables cross-cluster traffic hijack
A flaw was found in Submariner. This vulnerability allows a malicious cluster (spoke) to redirect network traffic from other connected clusters (peer clusters) by publishing a specially crafted network endpoint. The system fails to properly validate the network subnets provided by the malicious cluster, enabling it to declare arbitrary network ranges. Consequently, all network traffic intended for these arbitrary ranges from peer clusters will be rerouted through the attacker's tunnel, potentially leading to unauthorized information disclosure or network disruption.
Other sources
The broker-to-local sync hook shouldSyncRemoteEndpoint only rejects a remote Endpoint if its subnets overlap the local cluster's own subnets. It does not verify that Spec.ClusterID matches the broker SA that created the CR, that Spec.Subnets are within the CIDRs declared in that cluster's Cluster CR, or that Spec.Subnets do not overlap other remote clusters' subnets. The accepted subnets are installed verbatim as WireGuard AllowedIPs and as Libreswan --client rightSubnet. A malicious spoke can publish an Endpoint with subnets covering arbitrary CIDRs (including 10.0.0.0/8 or 0.0.0.0/0), causing all matching traffic from peer clusters to be routed into the attacker's tunnel.
Source: Project Glasswing AI-SAST audit of submariner-io/submariner. Finding ID: FIND-004 Assurance: executionproven
— Red Hat
Affected Software
Event History
Frequently Asked Questions
Which deployments are exposed to this issue?
Deployments with connected Submariner clusters are exposed when a malicious spoke cluster can publish a network endpoint that peer clusters consume. Peer clusters may then route traffic for attacker-declared network ranges through the malicious cluster's tunnel.
What does an attacker need to exploit it?
The attacker needs control of a connected cluster that can publish a specially crafted network endpoint with arbitrary subnet ranges. The CVSS vector indicates network reachability, low privileges, and no user interaction are required.
What is the likely impact on affected peer clusters?
Traffic intended for arbitrary ranges declared by the malicious cluster can be redirected through the attacker's tunnel. This can result in unauthorized information disclosure or network disruption.