CVE-2019-2137 in Android
Summary
by MITRE
In the endCall() function of TelecomManager.java, there is a possible Denial of Service due to a missing permission check. This could lead to local denial of access to Emergency Services with User execution privileges needed. User interaction is not needed for exploitation. Product: Android. Versions: Android-9. Android ID: A-132438333.
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Analysis
by VulDB Data Team • 08/01/2020
The vulnerability identified as CVE-2019-2137 resides within the TelecomManager.java component of Android 9.0 systems, specifically within the endCall() function where a critical permission validation gap exists. This flaw represents a denial of service vulnerability that stems from insufficient access controls, allowing unauthorized local processes to manipulate telephony services without proper authorization. The vulnerability falls under the category of improper permission checking as classified by CWE-284, which directly impacts the principle of least privilege and proper access control mechanisms. The issue manifests when an application attempts to terminate phone calls through the TelecomManager interface without verifying whether the calling process possesses the necessary permissions to perform such operations.
The technical exploitation of this vulnerability requires only local execution privileges and does not necessitate user interaction, making it particularly concerning from a security standpoint. An attacker with user-level access can leverage this flaw to disrupt emergency services functionality by invoking the endCall() method, potentially preventing legitimate emergency calls from being properly handled. This disruption occurs because the system fails to validate whether the calling application has the appropriate telephony permissions before executing the call termination sequence. The vulnerability is classified as a local privilege escalation vector within the context of Android's security model, where the missing permission check creates an attack surface that can be exploited to compromise the availability of critical telephony services.
The operational impact of CVE-2019-2137 extends beyond simple denial of service, as it can potentially prevent users from accessing emergency services during critical situations. When an application can bypass permission checks to terminate calls, it creates a scenario where emergency services may be rendered unavailable or disrupted, which could have life-threatening consequences. This vulnerability aligns with ATT&CK technique T1489, which covers denial of service attacks, and specifically targets the availability component of the CIA triad. The exploitation of this flaw could result in a complete disruption of telephony services on affected devices, affecting not only regular phone functionality but also emergency communication capabilities that rely on the underlying telephony framework.
Mitigation strategies for CVE-2019-2137 should focus on implementing proper permission validation within the TelecomManager endCall() function and ensuring that all telephony operations require appropriate authorization. Android security updates should enforce stricter access controls and validate caller permissions before executing sensitive telephony operations. System administrators and device manufacturers should apply the relevant security patches promptly to address this vulnerability, as the lack of user interaction requirements makes it particularly dangerous. The fix should involve implementing comprehensive permission checks that verify both the calling application's identity and its authorization level before allowing call termination operations, thereby preventing unauthorized access to critical telephony services and maintaining the integrity of emergency communication channels.