CVE-2024-21633: Critical Path Manipulation Vulnerability in Apktool

Overview

The CVE-2024-21633 vulnerability lies within Apktool, a popular tool used for reverse engineering Android APK files. This vulnerability affects versions 2.9.1 and prior of the tool. The vulnerability allows an attacker to manipulate resource file paths and potentially place files at any location on the system where Apktool is run. This could lead to potential system compromise or data leakage. This vulnerability is particularly concerning for environments where an attacker can write or overwrite any file the user has write access to, and either the user name is known or the current working directory is under the user folder.

Vulnerability Summary

CVE ID: CVE-2024-21633
Severity: High (7.8 CVSS)
Attack Vector: Local File System
Privileges Required: User level
User Interaction: Required
Impact: System compromise or data leakage

Affected Products

Product | Affected Versions

Apktool | 2.9.1 and prior

How the Exploit Works

The exploit takes advantage of the way Apktool infers resource file output paths based on their resource names. By manipulating these names, an attacker can influence where the output files are placed. This can allow an attacker to overwrite existing files or create new ones in sensitive areas of the file system, potentially leading to system compromise or data leakage.

Conceptual Example Code

The following is a conceptual example of how the vulnerability might be exploited:

import brut.androlib.*;
import brut.androlib.res.data.*;
// Create an instance of ApkDecoder (part of Apktool)
ApkDecoder decoder = new ApkDecoder();
// Set the APK file to be decoded
decoder.setApkFile(new File("path-to-malicious.apk"));
// Set the output directory to a directory controlled by the attacker
decoder.setOutDir(new File("malicious-output-directory"));
// Decode the APK
decoder.decode();

In this example, `path-to-malicious.apk` is an APK file crafted by an attacker to contain resource files with manipulated names. When decoded by Apktool, these resource files are placed in `malicious-output-directory`, which could be any location on the file system where the user running Apktool has write access.

Mitigation

Users of Apktool should apply the patch contained in commit d348c43b24a9de350ff6e5bd610545a10c1fc712 as soon as possible. If it is not possible to apply this patch immediately, using a Web Application Firewall (WAF) or an Intrusion Detection System (IDS) can provide temporary mitigation. However, these measures are not a substitute for applying the patch and should only be considered as a short-term solution.