CVE-2016-3708 in OpenShift Enterprise
Summary
by MITRE
Red Hat OpenShift Enterprise 3.2, when multi-tenant SDN is enabled and a build is run in a namespace that would normally be isolated from pods in other namespaces, allows remote authenticated users to access network resources on restricted pods via an s2i build with a builder image that (1) contains ONBUILD commands or (2) does not contain a tar binary.
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Analysis
by VulDB Data Team • 08/23/2022
The vulnerability described in CVE-2016-3708 represents a critical security flaw in Red Hat OpenShift Enterprise 3.2's multi-tenant Software Defined Networking implementation. This issue specifically affects environments where the software-defined network is enabled to enforce tenant isolation between different namespaces within the platform. The flaw occurs during the execution of source-to-image (s2i) build processes, which are fundamental components for creating containerized applications in OpenShift environments. When a user executes a build operation within a namespace that should normally be isolated from other namespaces, the vulnerability allows malicious actors to bypass the intended network restrictions and gain unauthorized access to network resources belonging to restricted pods.
The technical mechanism behind this vulnerability stems from how OpenShift handles s2i builds when specific conditions are met. The flaw manifests when a builder image contains ONBUILD commands or when the builder image lacks a tar binary, creating an execution path that circumvents the normal network isolation controls. This represents a classic case of privilege escalation through improper access control enforcement, where the system fails to properly validate or restrict the network access permissions during the build process. The vulnerability exploits the trust model between the build environment and the underlying network infrastructure, allowing an authenticated user to perform network reconnaissance and potentially execute malicious network operations against other tenant's pods.
From an operational impact perspective, this vulnerability significantly undermines the fundamental security principle of multi-tenancy that OpenShift Enterprise is designed to provide. Attackers can leverage this flaw to perform network-based reconnaissance, potentially accessing sensitive data or services hosted in other namespaces, conducting man-in-the-middle attacks, or even escalating their privileges within the cluster. The implications extend beyond simple information disclosure, as the ability to access restricted network resources could enable attackers to disrupt services, exfiltrate data, or establish persistent access points within the cluster environment. This vulnerability effectively breaks down the network segmentation that organizations rely on to isolate different workloads and teams within the same OpenShift infrastructure, creating a significant risk for multi-tenant deployments.
The vulnerability aligns with CWE-284 (Improper Access Control) and represents a specific instance of how container build processes can bypass security controls in cloud-native environments. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and lateral movement through compromised build processes. Organizations should implement immediate mitigations including disabling multi-tenant SDN when not required, enforcing strict image validation policies, and implementing additional network segmentation controls. The recommended approach involves ensuring that all builder images undergo rigorous security scanning, particularly verifying the presence of required binaries and proper execution of ONBUILD commands. Additionally, organizations should consider implementing network policy enforcement at multiple layers, including container runtime security controls and cluster-wide network access restrictions to prevent similar vulnerabilities from being exploited in other components of the OpenShift ecosystem.