CVE-2025-55198: Helm Helm DOS Vulnerability

CVE-2025-55198 Overview

CVE-2025-55198 affects Helm, the package manager for Kubernetes Charts. The vulnerability exists in versions prior to 3.18.5 and stems from improper type validation when parsing Chart.yaml and index.yaml files. A malformed YAML file can trigger a runtime panic in the Helm process, resulting in a denial-of-service condition. The maintainers resolved the issue in Helm 3.18.5. This flaw is tracked under [CWE-908: Use of Uninitialized Resource].

Critical Impact
A remote attacker can craft a malicious Chart.yaml or index.yaml file that causes Helm to panic when processed, disrupting chart installation, linting, or repository indexing workflows.

Affected Products

Helm versions prior to 3.18.5
Kubernetes tooling and CI/CD pipelines invoking vulnerable Helm binaries
Chart repository consumers processing untrusted index.yaml files

Discovery Timeline

2025-08-14 - CVE-2025-55198 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-55198

Vulnerability Analysis

Helm parses YAML metadata from two primary sources: Chart.yaml inside a chart archive and index.yaml served by chart repositories. When these files contain YAML nodes with unexpected types, such as a null entry where a structured object is expected, downstream code paths dereference the resulting nil pointer. The Go runtime then panics, terminating the Helm process.

The patched code in pkg/lint/rules/chartfile.go adds an explicit nil check inside validateChartMaintainer to reject empty maintainer entries before subsequent field access. A related change in pkg/chartutil/dependencies.go imports the fmt package to support additional validation logic. The fix converts an unhandled runtime crash into a controlled validation error.

Root Cause

The root cause is missing type validation during YAML deserialization. Helm assumed that decoded slice elements were non-nil struct pointers and accessed fields directly. When a YAML document produced a nil entry, this assumption failed and triggered a nil pointer dereference at runtime.

Attack Vector

Exploitation requires user interaction: a victim must run Helm against attacker-controlled chart content. Vectors include installing a malicious chart, adding a hostile repository, or running helm lint on a crafted Chart.yaml. The impact is limited to availability; confidentiality and integrity are not affected.

// Patched validation in pkg/lint/rules/chartfile.go
func validateChartMaintainer(cf *chart.Metadata) error {
	for _, maintainer := range cf.Maintainers {
		if maintainer == nil {
			return errors.New("a maintainer entry is empty")
		}
		if maintainer.Name == "" {
			return errors.New("each maintainer requires a name")
		} else if maintainer.Email != "" && !govalidator.IsEmail(maintainer.Email) {
			// ...
		}
	}
}
// Source: https://github.com/helm/helm/commit/ec5f59e2db56533d042a124f5bae54dd87b558e6

Detection Methods for CVE-2025-55198

Indicators of Compromise

Unexpected Helm process termination with Go runtime panic traces referencing chartutil or lint/rules packages
Chart.yaml or index.yaml files containing empty or null entries under maintainers, dependencies, or similar structured lists
Repeated failed helm install, helm lint, or helm repo update invocations against a specific repository or chart

Detection Strategies

Inventory all Helm binaries across build agents, developer workstations, and Kubernetes operators to identify versions below 3.18.5
Scan chart repositories and artifact registries for YAML files with malformed or nil structured entries prior to consumption
Monitor CI/CD job logs for Go panic signatures emitted by Helm during chart processing steps

Monitoring Recommendations

Alert on non-zero exit codes and stderr panic strings from Helm invocations in pipeline telemetry
Track additions of new chart repositories via helm repo add from untrusted sources
Correlate Helm crashes with the origin of the chart archive or index.yaml retrieved immediately before failure

How to Mitigate CVE-2025-55198

Immediate Actions Required

Upgrade Helm to version 3.18.5 or later on all workstations, servers, and CI/CD runners
Restrict chart sources to trusted, signed repositories and remove unused helm repo entries
Validate third-party Chart.yaml and index.yaml files against a schema before processing with Helm

Patch Information

The fix is committed in Helm at ec5f59e2db56533d042a124f5bae54dd87b558e6 and released in Helm 3.18.5. Refer to the Helm GitHub Security Advisory GHSA-f9f8-9pmf-xv68 and the upstream commit for full details.

Workarounds

Ensure YAML files conform to Helm's expected schema before invoking Helm commands
Pre-validate Chart.yaml and index.yaml with a YAML linter that flags null entries in structured lists
Isolate Helm execution in ephemeral containers so that a panic does not affect long-running orchestrators

bash

# Upgrade Helm to a fixed release
curl -fsSL -o get_helm.sh https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3
chmod 700 get_helm.sh
DESIRED_VERSION=v3.18.5 ./get_helm.sh
helm version --short