EUVD-2026-83043
GHSA-c8w2-fgvx-vhv4
Severity by source
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Authenticated tenant (PR:L) trivially injects a trusted header (AC:L) over the network; proxy asserts identity into downstream shards/other workspaces (S:C) yielding full admin read/write/delete (C:H/I:H/A:H).
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
Lifecycle Timeline
5DescriptionCVE.org
kcp is a Kubernetes-like control plane for form-factors and use-cases beyond Kubernetes and container workloads. Prior to 0.31.4 and 0.32.2, the kcp front-proxy does not remove inbound X-Remote-User, X-Remote-Group, or X-Remote-Extra-* identity headers before forwarding requests to shards. Any authenticated tenant can inject X-Remote-Group: system:masters, authorization.kcp.io/warrant, authentication.kcp.io/scopes, or a group used for per-workspace required-group gating, and the shard trusts these values as authenticated identity assertions. This allows cross-workspace impersonation, authorization bypass, and arbitrary reading, writing, or deletion of resources, secrets, RBAC data, APIExports, APIBindings, and LogicalClusters. This issue is fixed in versions 0.31.4 and 0.32.2.
Articles & Coverage 1
AnalysisAI
Cross-workspace impersonation and complete authorization bypass in kcp (kcp-dev) before 0.31.4 and 0.32.x before 0.32.2 let any authenticated tenant forge Kubernetes-style identity headers that the shard accepts as trusted authentication assertions. Because the front-proxy and the server localproxy forward inbound X-Remote-User, X-Remote-Group, and X-Remote-Extra-* headers without clearing them, an attacker with valid credentials for any single workspace can supply values such as X-Remote-Group: system:masters, authorization.kcp.io/warrant, authentication.kcp.io/scopes, or a group used for per-workspace required-group gating to read, write, or delete resources, secrets, RBAC data, APIExports, APIBindings, and LogicalClusters across the installation. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires the attacker to be an already-authenticated tenant of a kcp installation running a version prior to 0.31.4 or 0.32.2, sending requests through the kcp front-proxy (or the server localproxy). … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | This is a genuine top-tier priority, not a high-CVSS-but-low-real-risk case. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | Full exploit scenario with step-by-step reproduction available after sign-in. |
| Remediation | Upgrade to kcp 0.31.4 or 0.32.2 depending on your maintenance line - these are the vendor-released fixed versions and the only fully reliable remediation, since the code change (commits 7437cdcfec8f927d1a9bf1b2dd1e075d038e27ca and f913ee890fb2fd9fa78e50c43474b078bfb6aeff) makes ClearAuthHeaders run on every proxied request regardless of authentication state. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all kcp deployments and restrict network access to the front-proxy and localproxy to trusted management networks; apply ingress rules to strip or reject inbound X-Remote-User, X-Remote-Group, and X-Remote-Extra-* headers, and enable audit logging for authentication anomalies. …
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