Kyverno EUVD-2026-87680

Requires an authenticated low-privilege tenant with permission to create or modify namespaced Kyverno Policy resources that include an apiCall context entry with an attacker-controlled urlPath. Exploitation depends on Kyverno versions before 1.19.1 and a multi-tenant deployment where namespace isolation is the security boundary; the attacker crafts percent-encoded dot-segments so validation and execution interpret the path inconsistently. Limiting factors: authentication and namespaced-policy authoring rights are needed (PR:L), and the disclosure value hinges on the Kyverno controller ServiceAccount having broad cross-namespace read permissions (its typical configuration). No user interaction is required.

This is a genuine cross-tenant confidentiality issue rather than a high-CVSS-but-low-risk paper cut. The vendor CVSS 4.0 vector (AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:N/SC:H/SI:N/SA:N = 8.3) is internally consistent with the description: network-reachable Kubernetes API surface, low attack complexity, and only low tenant privileges required, with high confidentiality impact on a subsequent system (other tenants' namespaces) via a scope change (SC:H). No EPSS score, CISA KEV entry, or public exploit code was provided, so exploitation status is 'no public exploit identified at time of analysis' - the elevated score is driven by impact and ease, not by observed in-the-wild activity. The primary limiting factor is that the attacker must already be an authenticated low-privilege tenant with rights to create/modify namespaced Policy resources containing an apiCall context entry; this is a normal capability in multi-tenant Kyverno deployments, so in genuinely multi-tenant clusters the practical risk is meaningful. No key signals are outright conflicting, but the absence of EPSS/KEV/POC means priority should rest on deployment context (true multi-tenancy) rather than assumed mass exploitation.

A low-privilege tenant, restricted to its own namespace, authors a namespaced Kyverno Policy whose apiCall context entry sets urlPath with percent-encoded dot-segments (e.g. %2e%2e) so that Kyverno's namespace validation and its actual request execution interpret the path differently. When the policy executes, Kyverno issues the API request using its admission controller ServiceAccount, reading Secrets, ConfigMaps, or other resources from namespaces the tenant should not access. No public proof-of-concept was referenced, but the technique is straightforward path-normalization abuse.