CVE-2025-32387 in Helm
Summary
by MITRE • 04/10/2025
Helm is a package manager for Charts for Kubernetes. A JSON Schema file within a chart can be crafted with a deeply nested chain of references, leading to parser recursion that can exceed the stack size limit and trigger a stack overflow. This issue has been resolved in Helm v3.17.3.
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Analysis
by VulDB Data Team • 09/03/2025
The vulnerability identified as CVE-2025-32387 affects Helm, a widely-used package manager for Kubernetes that facilitates the deployment and management of applications through reusable chart templates. This security flaw resides within Helm's handling of JSON Schema files that are part of chart definitions, specifically targeting the parser's recursive processing capabilities. The vulnerability manifests when a chart contains a JSON Schema with deeply nested reference chains that can cause the parser to enter infinite recursion, ultimately exhausting available stack memory and resulting in a stack overflow condition that can crash the Helm process and potentially disrupt application deployment workflows.
The technical implementation of this vulnerability stems from insufficient recursion depth validation within Helm's JSON Schema parser. When processing chart files, Helm traverses reference chains in JSON Schema documents to validate structure and data types, but fails to implement adequate safeguards against excessively deep nesting. This parsing behavior aligns with CWE-674, which describes "Uncontrolled Recursion" in software systems, where recursive algorithms lack proper termination conditions or depth limits. The flaw operates at the parser level within Helm's chart processing pipeline, making it particularly dangerous as it can be triggered during any chart validation or installation operation that involves schema processing.
The operational impact of this vulnerability extends beyond simple service disruption to potentially enable denial of service attacks against Kubernetes cluster management systems. An attacker who can influence chart content or deployment processes could craft malicious charts that trigger stack overflow conditions, thereby preventing legitimate chart installations or upgrades. This issue particularly affects environments where Helm charts are used extensively for application deployment, as any chart processing operation could become a potential attack vector. The vulnerability's severity is amplified in automated deployment pipelines where chart validation occurs frequently, potentially causing cascading failures across multiple deployment targets.
Mitigation strategies for CVE-2025-32387 primarily involve upgrading to Helm version 3.17.3 or later, which includes proper recursion depth limiting mechanisms within the JSON Schema parser. Organizations should also implement chart validation policies that restrict the complexity of schema definitions and monitor for unusual nesting patterns in chart files. Additionally, security teams should consider implementing runtime protections such as stack limit enforcement and process isolation for Helm operations to prevent exploitation. The remediation approach aligns with ATT&CK technique T1499.004, which covers "Utilities: File System Permissions Modification," as proper access controls and validation mechanisms can prevent unauthorized chart modifications that might contain malicious schema structures. Organizations should also conduct regular vulnerability assessments of their Helm chart repositories to identify and remediate potentially vulnerable chart configurations before they can be exploited in production environments.