The Android operating system is constantly updating and improving its various components to ensure better security and functionality. One such component is the MmsProvider.java class, which is responsible for handling multimedia messages (MMS) on Android devices. However, a recent update has revealed a critical vulnerability, identified as CVE-2022-20453, that has the potential to cause severe issues for affected devices.

This long read will dive into the details of this vulnerability, outline the problematic code snippet, provide links to original references, and explain the possible exploitation of this flaw. The content is written in simple American English to cater to developers and enthusiasts of varying levels of understanding.

Detailed Description of CVE-2022-20453

CVE-2022-20453 refers to an error in the MmsProvider.java update, specifically regarding a possible constriction of directory permissions as a result of a path traversal vulnerability. The path traversal error can lead to a local denial of service (DoS) of SIM recognition, effectively rendering the device unable to recognize the SIM card. To successfully exploit this vulnerability, no additional execution privileges are required; however, user interaction is necessary.

The affected Android versions include Android-10, Android-11, Android-12, Android-12L, and Android-13. The Android ID associated with this vulnerability is A-240685104.

Code Snippet

The code snippet below demonstrates an example of incorrect validation in the MmsProvider.java file, potentially leading to a path traversal vulnerability.

public ParcelFileDescriptor openFile(Uri uri, String mode) {
  File file = new File(getContext().getDir("mms", ), uri.getPath());
  ParcelFileDescriptor pfd = ParcelFileDescriptor.open(file, ParcelFileDescriptor.MODE_READ_WRITE);
  return pfd;
}

In the snippet above, the uri.getPath() method retrieves the file path without proper validation, allowing for unintended access to directories outside the intended scope.

1. Android Security Bulletin: https://source.android.com/security/bulletin
2. CVE Details: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2022-20453

Exploit Details

To exploit the CVE-2022-20453 vulnerability, an attacker must first trick the user into interacting with a malicious multimedia message (MMS) or a crafted application. This user interaction could potentially lead to the execution of the vulnerability, causing a local denial of service of SIM recognition. The device would then be unable to recognize the SIM card, effectively disabling the device's cellular functionalities.

Mitigation

While no official patch has been released for CVE-2022-20453 as of yet, developers and users should be cautious when handling multimedia messages, especially from unknown sources, and refrain from downloading untrusted applications. By exercising caution and being vigilant about the content your device interacts with, the chances of successful exploitation can be significantly reduced.

Additionally, developers creating MMS handling applications or using the MmsProvider.java class in their projects should implement rigorous input validation to prevent potential path traversal attacks.

Conclusion

CVE-2022-20453 is a severe vulnerability affecting the Android MMS provider class MmsProvider.java. This vulnerability allows a constriction of directory permissions, potentially leading to a local denial of service of SIM recognition. To protect their devices and applications, users and developers should be cautious handling MMS messages from unknown sources and ensure strict input validation is enforced in their code. By remaining vigilant, the Android community can work together to mitigate the potential risks associated with this vulnerability.

Timeline

Published on: 11/08/2022 22:15:00 UTC
Last modified on: 11/09/2022 16:28:00 UTC