CVE-2026-122319 in Kyverno
Summary
by MITRE • 11/05/2026
Kyverno before 1.19.2 contains a denial-of-service vulnerability in the In and NotIn operators that allows attackers to crash the policy engine via an unchecked type assertion. Attackers can submit resources whose JMESPath-evaluated values yield arrays of integers, booleans, or mixed types, triggering a panic that disrupts admission control and policy enforcement.
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Analysis
by VulDB Data Team • 11/05/2026
The vulnerability identified in Kyverno versions prior to 1.19.2 represents a critical denial-of-service condition rooted in improper input validation within the policy engine's evaluation logic. Specifically, the flaw resides in the implementation of the In and NotIn operators, which are designed to check for membership or non-membership of values within lists during rule execution. These operators rely on type assertions to ensure that the data types being compared are compatible before performing logical operations. However, due to a lack of rigorous type checking prior to these assertions, the system fails to handle scenarios where JMESPath expressions evaluate to arrays containing integers, booleans, or mixed-type elements in contexts expecting uniform types. This oversight allows an attacker who has permission to submit resources for admission control processing to trigger a runtime panic within the Kyverno controller pod.
From a technical perspective, this issue is classified under CWE-20 Improper Input Validation and CWE-754: Improper Check for Unusual or Exceptional Conditions. The root cause lies in the Go programming language's strict typing system where an invalid type assertion results in a panic if not properly handled with a comma-ok idiom or similar defensive coding practices. When JMESPath processes resource data, it may return complex structures including arrays of heterogeneous types depending on how the source YAML manifests are constructed. If such malformed input is passed to the In or NotIn operators without prior validation that all elements in the array match the expected type for comparison, the underlying Go runtime throws a panic exception. This causes the Kyverno process to terminate abruptly, leading to immediate service disruption rather than graceful error handling or rejection of the invalid policy rule.
The operational impact of this vulnerability is severe within Kubernetes environments relying on Kyverno for admission control and continuous compliance monitoring. Since Kyverno operates as an admission webhook controller, its unavailability directly impacts the cluster's ability to enforce security policies during resource creation and modification requests. A successful exploitation results in a denial-of-service condition where new workloads cannot be deployed until the Kyverno pod is restarted by Kubernetes' self-healing mechanisms. During this downtime window, there is no policy enforcement active for admission-controlled resources, potentially allowing unauthorized or non-compliant configurations to enter the cluster if other controls are not present. Furthermore, repeated crashes can lead to resource exhaustion on the node hosting the Kyverno deployment due to rapid restart loops, degrading overall cluster stability and performance.
This vulnerability aligns with MITRE ATT&CK technique T1496: Resource Hijacking in the context of denial-of-service impacts, although it is more accurately described as a service disruption vector rather than direct resource hijacking for cryptomining or compute abuse. It also relates to CWE-787 Out-of-bounds Write if one considers memory corruption aspects, but primarily falls under input validation failures that lead to application crashes. The attack requires only standard API access permissions to submit resources, making it accessible to any user with create privileges on the affected resource types within namespaces where Kyverno policies are applied.
Mitigation strategies focus heavily on upgrading the Kyverno installation to version 1.19.2 or later, which includes patches for these type assertion checks. Administrators should verify their current deployment versions and apply updates through standard Helm charts or Kubernetes manifests as appropriate for their environment. In addition to patching, organizations can implement network policies to restrict access to the admission webhook endpoints from untrusted namespaces until upgrades are completed. Monitoring logs for panic stack traces in Kyverno pods serves as an effective detection mechanism for potential exploitation attempts. Long-term resilience involves adopting defense-in-depth principles by combining policy engines with other security controls such as OPA Gatekeeper or native Kubernetes RBAC restrictions, ensuring that a failure in one component does not result in total loss of admission control capabilities. Regular auditing of JMESPath expressions used in custom policies can also help identify complex type interactions that might trigger similar issues in future versions.