melange QEMU runner konnte Dateien außerhalb des Arbeitsbereichsverzeichnisses in chainguard.dev/melange schreiben

The core of this vulnerability lies in Melange's QEMU runner's file handling logic. An attacker, by crafting malicious inputs, can bypass workspace directory restrictions and write files to arbitrary locations on the host system. This could involve overwriting critical system files, injecting malicious scripts, or deploying malware. The potential impact extends beyond simple data corruption; successful exploitation could grant an attacker complete control over the affected system, enabling data theft, privilege escalation, and lateral movement within the network. The blast radius depends on the system's permissions and network connectivity.

Organizations utilizing Chainguard Melange for container image building or other QEMU-based workflows are at risk. This includes DevOps teams, CI/CD pipelines, and environments where Melange is integrated into automated build processes. Specifically, those relying on older versions of Melange (prior to 0.40.3) are vulnerable.

• go / supply-chain: Inspect Melange's source code for file path manipulation functions. Look for instances where user-supplied input is directly used to construct file paths without proper sanitization.

// Example: Check for direct path concatenation
if strings.Contains(filepath.Clean(userInput), "../") {
    // Potential vulnerability
}

• generic web: Monitor access logs for unusual file creation attempts outside the expected workspace directory. Look for patterns indicative of path traversal attacks.

# Example: grep for path traversal attempts in access logs
grep "../" /var/log/nginx/access.log

1. 2026-02-05Disclosure

   disclosure

1. Reserviert2026-01-27
2. Veröffentlicht2026-02-05
3. EPSS aktualisiert2026-03-23

The primary mitigation is to immediately upgrade Chainguard Melange to version 0.40.3 or later. This version contains the necessary fix to prevent unauthorized file writes. If upgrading is not immediately feasible, consider implementing stricter workspace directory permissions to limit the potential impact of a successful exploit. Additionally, monitor file system activity for unexpected writes outside the intended workspace. While a WAF is unlikely to directly address this, reviewing and hardening QEMU configurations can reduce the attack surface. There are no specific Sigma or YARA rules available at this time, but monitoring for unusual file creation events is recommended.