CVE-2025-55205 is a critical-severity incorrect authorization vulnerability in github.com/projectcapsule/capsule (go), affecting versions < 0.10.4. It is fixed in 0.10.4.
Summary A namespace label injection vulnerability in Capsule v0.10.3 allows authenticated tenant users to inject arbitrary labels into system namespaces (kube-system, default, capsule-system), bypassing multi-tenant isolation and potentially accessing cross-tenant resources through TenantResource selectors. This vulnerability enables privilege escalation and violates the fundamental security boundaries that Capsule is designed to enforce. Details The vulnerability exists in the namespace validation webhook logic located in pkg/webhook/namespace/validation/patch.go:60-77. The critical flaw is in the conditional check that only validates tenant ownership when a namespace already has a tenant label: Root Cause Analysis: Missing Default Protection: System namespaces (kube-system, default, capsule-system) do not have the capsule.clastix.io/tenant label by default Bypass Logic: The webhook only enforces tenant ownership validation when the target namespace already belongs to a tenant Unrestricted Label Injection: Authenticated users can inject arbitrary labels into unprotected namespaces Attack Vector Path: This mirrors the CVE-2024-39690 attack pattern but uses label injection instead of ownerReference manipulation: CVE-2024-39690: ownerReference(user-controlled) → tenant.Status.Namespaces(system state) → quota/permission check(auth policy) → namespace hijacking This vulnerability: Label injection(user-controlled) → Namespace selector(system matching) → TenantResource/Quota check(auth policy) → cross-tenant resource access PoC Prerequisites: Minikube cluster with Capsule v0.10.3 installed Authenticated tenant user with basic RBAC permissions Step 1: Environment Setup Step 2: Label Injection Attack Step 3: Exploitation via TenantResource Step 4: Verification of Impact Automated Testing Script: A complete vulnerability verification script is available that tests: Label injection into multiple system namespaces TenantResource exploitation Cross-tenant resource access verification Impact assessment and cleanup Impact Vulnerability Type: Authorization Bypass / Privilege Escalation Who is Impacted: Multi-tenant Kubernetes clusters using Capsule v0.10.3 and potentially earlier versions Organizations relying on Capsule for tenant isolation and resource governance Cloud service providers offering Kubernetes-as-a-Service with Capsule-based multi-tenancy Security Impact: Multi-tenant Isolation Bypass: Attackers can access resources from other tenants or system namespaces Privilege Escalation: Tenant users can gain access to cluster-wide resources and sensitive system components Data Exfiltration: Potential access to secrets, configmaps, and other sensitive data in system namespaces Resource Quota Bypass: Ability to consume resources outside assigned tenant boundaries Policy Circumvention: Bypass network policies, security policies, and other tenant-level restrictions Real-world Exploitation Scenarios: Access to kube-system secrets containing cluster certificates and service account tokens Modification or replication of critical system configurations Cross-tenant data access in shared clusters Potential cluster-wide compromise through system namespace access Severity: High - This vulnerability fundamentally breaks the multi-tenant security model that Capsule is designed to provide, allowing authenticated users to escape their tenant boundaries and access system-level resources.
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
CVE-2025-55205 has a CVSS score of 9.0 (Critical). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment.
A fixed version is available (0.10.4). Upgrading removes the vulnerable code path.
go
github.com/projectcapsule/capsule (< 0.10.4)github.com/projectcapsule/capsule → 0.10.4 (go)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Upgrade github.com/projectcapsule/capsule to 0.10.4 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2025-55205 is a critical-severity incorrect authorization vulnerability in github.com/projectcapsule/capsule (go), affecting versions < 0.10.4. It is fixed in 0.10.4. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
CVE-2025-55205 has a CVSS score of 9.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
github.com/projectcapsule/capsule (go) versions < 0.10.4 is affected.
Yes. CVE-2025-55205 is fixed in 0.10.4. Upgrade to this version or later.
Whether CVE-2025-55205 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade github.com/projectcapsule/capsule to 0.10.4 or later.