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Insecure file upload - DLL Injection

Description​

The application does not properly validate the DLL files, allowing the injection of malicious DLLS

Impact​

Inject backdoors, virus, or other types of malicious files into the application

Recommendation​

  • Verify with an antivirus that the imported DLLs do not contain virus, backdoors or potentially harmful information
  • Define a white-list of allowed DLLs and their respective integrity hashes

Threat​

Anonymous attacker from local machine

Expected Remediation Time​

⌚ 20 minutes.

Score​

Default score using CVSS 3.1. It may change depending on the context of the vulnerability.

Base​

  • Attack vector: L
  • Attack complexity: L
  • Privileges required: N
  • User interaction: N
  • Scope: U
  • Confidentiality: N
  • Integrity: L
  • Availability: N

Temporal​

  • Exploit code madurity: P
  • Remediation level: U
  • Report confidence: C

Result​

  • Vector string: CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N/E:P/RL:U/RC:C
  • Score:
    • Base: 4.0
    • Temporal: 3.8
  • Severity:
    • Base: Medium
    • Temporal: Low

Code Examples​

Compliant code​

The application performs server side validation for all inputs

using System;
using System.Reflection;
public partial class WebForm : System.Web.UI.Page {
  protected void Page_Load(object sender, EventArgs e) {
    string input = Request.Form["in"];
    string cleanInput = clearRawUserInput(input);
    byte[] rawAssembly = Convert.FromBase64String(cleanInput);
    Assembly.Load(rawAssembly);
  }
}

Non compliant code​

The application does not verify on the server side the inputs before a file upload

using System;
using System.Reflection;
public partial class WebForm : System.Web.UI.Page {
  protected void Page_Load(object sender, EventArgs e) {
    string input = Request.Form["in"];
    byte[] rawAssembly = Convert.FromBase64String(input);
    Assembly.Load(rawAssembly);
  }
}

Requirements​

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