Overview
In this post, we will be shedding light on the recently discovered vulnerability identified as CVE-2025-55205. This vulnerability is present in Capsule, a multi-tenancy and policy-based framework for Kubernetes, and impacts versions up to and including 0.10.3. The severity of this vulnerability is high and it poses a significant threat to the fundamental security boundaries that Capsule is designed to enforce.
This vulnerability, if exploited, could allow authenticated tenant users to bypass multi-tenant isolation and potentially access cross-tenant resources. This could lead to system compromise or data leakage, thereby posing a critical risk to organizations using this framework.
Vulnerability Summary
CVE ID: CVE-2025-55205
Severity: High (CVSS 9.0)
Attack Vector: Network
Privileges Required: Low
User Interaction: Required
Impact: Potential system compromise or data leakage
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Product | Affected Versions
Capsule Kubernetes Framework | 0.10.3 and earlier
How the Exploit Works
The vulnerability arises due to an issue in the handling of namespace labels within the Capsule Kubernetes framework. An authenticated user can exploit this vulnerability by injecting arbitrary labels into system namespaces, such as kube-system, default, or capsule-system. This action bypasses the multi-tenant isolation, giving the attacker potential access to cross-tenant resources through TenantResource selectors.
Conceptual Example Code
Below is a conceptual example of how the vulnerability might be exploited. This is a hypothetical HTTP request that might be used to execute the attack.
POST /api/v1/namespaces/kube-system HTTP/1.1
Host: target.example.com
Authorization: Bearer <token>
Content-Type: application/json
{ "metadata": { "labels": { "malicious_label": "injected_value" } } }In this example, the attacker is making a POST request to the kube-system namespace, injecting a malicious label into the system.
Mitigation Guidance
The vulnerability has been fixed in Capsule version 0.10.4. Therefore, users are strongly recommended to update to this version or later as soon as possible. In the interim, a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can be used for temporary mitigation. Regularly monitoring system logs for any unusual activities or unauthorized access attempts can also help in early detection of potential threats.