CVE-2021-1031 in Android
Summary
by MITRE • 12/15/2021
In cancelNotificationsFromListener of NotificationManagerService.java, there is a possible way to determine whether an app is installed, without query permissions, due to side channel information disclosure. This could lead to local information disclosure with no additional execution privileges needed. User interaction is not needed for exploitation.Product: AndroidVersions: Android-12Android ID: A-194697004
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Analysis
by VulDB Data Team • 12/22/2021
The vulnerability identified as CVE-2021-1031 resides within the Android notification system, specifically in the cancelNotificationsFromListener method of NotificationManagerService.java. This flaw represents a side-channel information disclosure vulnerability that allows unauthorized determination of application installation status without requiring explicit query permissions. The issue manifests through the notification management service's handling of notification cancellation requests, where the system's response behavior inadvertently reveals information about installed applications. The vulnerability exists in Android 12 and affects the core notification subsystem that manages how applications interact with system notifications. This represents a significant privacy and security concern as it enables attackers to gather information about the application landscape on a device without proper authorization.
The technical implementation of this vulnerability stems from the notification manager service's inconsistent handling of notification cancellation requests for applications that may or may not be installed. When an application attempts to cancel notifications from a listener, the service responds differently based on whether the target application exists on the device. This differential response creates a timing or behavioral side channel that can be exploited to infer application installation status. The flaw occurs because the system does not properly normalize its response behavior regardless of whether the target application exists, leading to observable differences in execution paths. This type of information disclosure vulnerability aligns with CWE-203, which addresses side-channel information leakage, and demonstrates how seemingly benign system operations can expose sensitive data through indirect means.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with a method to enumerate installed applications without requiring additional privileges or user interaction. An attacker could potentially use this information to tailor more sophisticated attacks, such as targeting specific applications with known vulnerabilities or conducting reconnaissance for privilege escalation attempts. The lack of user interaction requirement makes this vulnerability particularly concerning as it can be exploited automatically through background processes or malicious applications. This type of local information disclosure could enable attackers to build detailed profiles of device configurations, potentially leading to more targeted attacks or exploitation of application-specific vulnerabilities. The vulnerability operates at the system level within the notification manager service, making it accessible to any application that can trigger notification cancellation requests.
Mitigation strategies for CVE-2021-1031 should focus on implementing consistent response behaviors within the notification management service, ensuring that all notification cancellation requests produce identical responses regardless of application installation status. Android security updates addressed this issue by modifying the cancelNotificationsFromListener method to normalize its behavior and eliminate the side-channel information leakage. System administrators should ensure that devices are updated to the latest security patches, which include modifications to the notification manager service to prevent differential response behaviors. The fix typically involves implementing proper access control checks and ensuring that notification cancellation operations do not expose information about application existence. Organizations should also consider monitoring notification-related system calls for unusual patterns that might indicate exploitation attempts. This vulnerability highlights the importance of secure coding practices in system-level services and the need for comprehensive security reviews of inter-component communication mechanisms. The remediation approach aligns with ATT&CK technique T1083, which addresses directory and file system discovery, as it prevents unauthorized enumeration of installed applications through indirect means.