CVE-2025-53547: Helm Package Manager RCE Vulnerability

CVE-2025-53547 Overview

CVE-2025-53547 is a local code execution vulnerability in Helm, the popular package manager for Kubernetes Charts. The vulnerability exists in how Helm handles symlinked Chart.lock files during dependency updates. A specially crafted Chart.yaml file, combined with a symlinked Chart.lock file, can lead to arbitrary code execution on the local system when dependencies are updated.

The attack exploits the fact that fields from Chart.yaml are carried over to Chart.lock when dependencies are updated. By crafting malicious content in these fields and symlinking Chart.lock to an executable file (such as .bashrc or a shell script), an attacker can inject arbitrary commands that execute when the target file is sourced or run. While Helm did warn about symlinked files, it did not halt execution, allowing the attack to proceed.

Critical Impact

Successful exploitation allows attackers to execute arbitrary code on systems where users update Helm chart dependencies, potentially leading to complete system compromise in Kubernetes deployment environments.

Affected Products

• Helm versions prior to 3.18.4
• All platforms where Helm is deployed for Kubernetes chart management
• CI/CD pipelines that automatically update Helm dependencies

Discovery Timeline

• 2025-07-08 - CVE-2025-53547 published to NVD
• 2025-09-03 - Last updated in NVD database

Technical Details for CVE-2025-53547

Vulnerability Analysis

This vulnerability represents a classic symlink attack (CWE-94: Improper Control of Generation of Code) that leverages Helm's dependency management workflow. When a user runs helm dependency update on a chart, Helm reads the Chart.yaml file and generates or updates the corresponding Chart.lock file with dependency information.

The root issue lies in Helm's failure to enforce security boundaries when the Chart.lock file is a symbolic link to another file on the filesystem. An attacker who can control the contents of a Chart.yaml file and create a symlink for Chart.lock can inject executable content into critical system files.

The attack requires local access or the ability to convince a user to clone and process a malicious Helm chart. Once triggered, the injected code executes with the privileges of the user running Helm, potentially providing initial access or escalating privileges in development and CI/CD environments.

Root Cause

The vulnerability stems from insufficient validation of the Chart.lock file path before writing dependency information. Helm's previous behavior was to warn users about symlinked files but continue processing, creating a window for exploitation. The lack of strict symlink resolution and path canonicalization allowed write operations to traverse outside the intended chart directory structure.

Attack Vector

The attack requires local access and user interaction. An attacker must craft a malicious Helm chart containing:

1. A Chart.yaml file with specially crafted field values containing shell commands
2. A Chart.lock file symlinked to an executable target (e.g., ~/.bashrc, ~/.profile, or a shell script)

When the victim runs helm dependency update on the malicious chart, the lock file content is written to the symlinked target file. The malicious commands embedded in the chart metadata are then executed when the target file is sourced or run.

The attack is particularly dangerous in automated CI/CD pipelines where charts from untrusted sources may be processed, or in scenarios where developers routinely fetch and update community-maintained charts.

Detection Methods for CVE-2025-53547

Indicators of Compromise

• Unexpected symlinks present in Helm chart directories, particularly Chart.lock pointing outside the chart directory
• Modified shell configuration files (.bashrc, .profile, .zshrc) with unexpected Helm-related content
• Unusual process execution following helm dependency update commands
• Chart repositories containing suspicious symlink structures

Detection Strategies

• Monitor file system operations during Helm chart processing for symlink traversal attempts
• Implement pre-commit hooks to detect symlinked files in Helm chart repositories before processing
• Use file integrity monitoring on critical configuration files in development environments
• Audit Helm chart sources for unusual Chart.yaml field values containing shell metacharacters

Monitoring Recommendations

• Enable verbose logging for Helm operations to capture symlink warnings
• Implement alerting on file modifications to user shell configuration files during Helm operations
• Deploy endpoint detection and response (EDR) solutions to monitor process chains originating from Helm
• Review CI/CD pipeline logs for unusual Helm warning messages about symlinked files

How to Mitigate CVE-2025-53547

Immediate Actions Required

• Upgrade Helm to version 3.18.4 or later immediately
• Audit existing Helm charts in your environment for suspicious symlinks
• Review any charts sourced from untrusted repositories before processing
• Verify file integrity of shell configuration files on systems where Helm is used

Patch Information

The vulnerability has been addressed in Helm version 3.18.4. The fix modifies Helm's behavior to properly handle symlinked files by refusing to write to them rather than just warning. Users should upgrade using their standard package manager or by downloading the latest release directly from the official Helm releases page.

The security fix is tracked in the GitHub Security Advisory and the specific commit implementing the fix can be reviewed at the Helm GitHub repository.

Workarounds

• Manually inspect charts for symlinks before running helm dependency update
• Use containerized or sandboxed environments when processing untrusted Helm charts
• Implement file system monitoring to detect symlink creation in chart directories
• Restrict Helm operations in CI/CD pipelines to verified and trusted chart sources only

# Check for symlinks in Helm chart directories before processing
find ./charts -type l -ls

# Upgrade Helm to patched version
helm version
# If below 3.18.4, upgrade via your package manager or:
curl https://raw.githubusercontent.com/helm/helm/main/scripts/get-helm-3 | bash