CVE-2026-25143
📋 TL;DR
This vulnerability allows attackers to execute arbitrary shell commands on the build host by injecting shell metacharacters into melange's patch pipeline inputs. It affects users of melange from version 0.10.0 to 0.40.2 who build apk packages using declarative pipelines. Attackers who can influence patch-related inputs (through CI/CD systems, pull requests, or configuration files) can exploit this to run commands with melange build process privileges.
💻 Affected Systems
- melange
📦 What is this software?
Melange by Chainguard
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of the build host, allowing attackers to steal credentials, modify build artifacts, pivot to other systems, or establish persistent backdoors in the build infrastructure.
Likely Case
Unauthorized command execution leading to data exfiltration, build artifact tampering, or lateral movement within the build environment.
If Mitigated
Limited impact due to restricted build environment, network segmentation, and minimal privileges assigned to melange processes.
🎯 Exploit Status
Exploitation requires ability to influence patch pipeline inputs, which is feasible in CI/CD environments, pull request workflows, or build-as-a-service scenarios. The vulnerability is straightforward to exploit once input control is achieved.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.40.3
Vendor Advisory: https://github.com/chainguard-dev/melange/security/advisories/GHSA-rf4g-89h5-crcr
Restart Required: No
Instructions:
1. Update melange to version 0.40.3 or later using your package manager. 2. For source installations: git clone the repository and checkout the patched commit bd132535cd9f57d4bd39d9ead0633598941af030. 3. Rebuild melange from source if necessary. 4. Verify the update with 'melange version'.
🔧 Temporary Workarounds
Input Sanitization
linuxImplement strict input validation and sanitization for all patch pipeline inputs to reject shell metacharacters.
# Example input validation script
# Reject inputs containing shell metacharacters
if [[ "$INPUT" =~ [\`\$\|\&\;\>\<] ]]; then
echo "Invalid input detected"
exit 1
fi
Restrict Build Environment
linuxRun melange in isolated containers with minimal privileges and network access.
# Run melange in Docker with restricted capabilities
docker run --cap-drop=ALL --security-opt=no-new-privileges -v $(pwd):/work chainguard/melange:latest build
🧯 If You Can't Patch
- Disable or restrict use of patch pipelines in melange configurations
- Implement strict access controls on who can submit pull requests or modify build configurations
🔍 How to Verify
Check if Vulnerable:
Check melange version with 'melange version' or 'melange --version'. If version is between 0.10.0 and 0.40.2 inclusive, the system is vulnerable.Check Version:
melange versionVerify Fix Applied:
After updating, verify version is 0.40.3 or higher. Test patch pipeline functionality with controlled inputs containing shell metacharacters to ensure they are properly sanitized.📡 Detection & Monitoring
Log Indicators:
- Unexpected shell commands in melange build logs
- Unusual process execution from melange build context
- Failed patch pipeline executions with error messages about invalid characters
Network Indicators:
- Unexpected outbound connections from build hosts during melange execution
- DNS queries to suspicious domains from build processes
SIEM Query:
process.name="melange" AND (command_line CONTAINS "$" OR command_line CONTAINS "`" OR command_line CONTAINS ";")