A new vulnerability, referenced as CVE-2023-40106, has been recently identified in the Android Open Source Project (AOSP) codebase. This vulnerability resides in the sanitizeSbn() function of the NotificationManagerService.java file and could lead to local escalation of privilege. This post aims to provide an in-depth understanding of this vulnerability, its exploit details, and its potential impact.

Description

The CVE-2023-40106 vulnerability is unique because it does not require user interaction for exploitation, nor does it require additional execution privileges. The primary cause of this vulnerability is what security researchers refer to as "Broadcast Activity Launch (BAL) Bypass" in the Android system.

Now, let's delve deeper into the NotificationManagerService.java codebase to better comprehend how the vulnerability operates.

Code Snippet

The following code snippet presents the sanitizeSbn() function within the NotificationManagerService.java file, which is responsible for the vulnerability:

private void sanitizeSbn(PostedNotification sbn) {
    if (sbn.notification.isForegroundService()) {
        enforceForegroundNotificationRule(sbn, true);
    }

    if (sbn.notification.getCollapseActionButton()) {
        sbn.notification.setAutoCancelButton(false);
    }

    // ActivityManager server-side will also apply some of these policies.
    if (sbn.isLaunchingActivity()) {
        enforceActivityLaunchActivationRule(sbn, true);
    }

    // Make sure the notification is appropriate for the device state.
    ...
}

This function is responsible for sanitizing input values in the notification, like making sure the notification is suitable for the device state and enforcing rules for foreground notifications, activity launch activations, and automatic cancellation.

Exploit Details

The potential exploit targeting this vulnerability operates by bypassing the BAL security mechanism and launching an activity from the background. This could lead to local escalation of privilege, allowing malicious actors to gain unauthorized access to sensitive user data.

An attacker could exploit this vulnerability by crafting a malicious app that runs in the background and takes advantage of the BAL Bypass mechanism to execute unauthorized activities or gain unauthorized access to users' data. The following steps outline an attack scenario:

The malicious app runs in the background and is initialized without user interaction.

3. Once initialized, the app leverages the CVE-2023-40106 vulnerability to execute unauthorized activities or exfiltrate sensitive data.

Original References

The discovery of this vulnerability was made public through multiple security research channels, some of which include the following resources:

Android Open Source Project (AOSP) codebase

- NotificationManagerService.java

MITRE's Common Vulnerabilities and Exposures (CVE) database

- CVE-2023-40106

National Vulnerability Database (NVD)

- CVE-2023-40106 Detail

Conclusion

The CVE-2023-40106 vulnerability in the SanitizeSbn() function of NotificationManagerService.java presents a serious threat due to its potential for local escalation of privilege through no user interaction or additional execution privileges. It is crucial for developers, security researchers, and Android users alike to remain vigilant in addressing such vulnerabilities and ensuring they are patched promptly. As always, security is an ongoing process that requires the proactive efforts of all parties involved.

Timeline

Published on: 02/15/2024 23:15:08 UTC
Last modified on: 02/16/2024 13:37:55 UTC