CVE-2021-25397 in Smart Phone
Summary
by MITRE • 06/11/2021
An improper access control vulnerability in TelephonyUI prior to SMR MAY-2021 Release 1 allows local attackers to write arbitrary files of telephony process via untrusted applications.
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Analysis
by VulDB Data Team • 06/14/2021
The vulnerability identified as CVE-2021-25397 represents a critical access control flaw within the TelephonyUI component of Android systems prior to the May 2021 security patch release. This issue resides in the telephony user interface module that handles telephony-related functionalities and communications within the Android operating system. The vulnerability stems from inadequate permission checks and validation mechanisms that allow malicious applications with minimal privileges to escalate their access and manipulate telephony processes through file system operations.
The technical flaw manifests as a lack of proper input validation and privilege separation within the TelephonyUI framework. Attackers can exploit this weakness by crafting untrusted applications that attempt to write arbitrary files to locations typically restricted to telephony processes. This improper access control vulnerability falls under the CWE-284 category of "Improper Access Control" which specifically addresses insufficient restrictions on system resources and operations. The vulnerability exists because the system fails to properly authenticate or authorize file operations that should be restricted to system-level components or processes with elevated privileges.
From an operational perspective, this vulnerability poses significant risks to device security and user privacy. Local attackers who can install malicious applications on a device gain the ability to modify telephony-related files and potentially interfere with cellular communications, call logging, SMS functionality, or other telephony services. The impact extends beyond simple file manipulation as these modifications could potentially disrupt network connectivity, enable unauthorized surveillance, or provide attackers with persistent access points within the device. The vulnerability particularly affects devices running Android versions prior to the May 2021 security update, making older devices and those not promptly patched especially vulnerable to exploitation.
The attack vector for this vulnerability requires local access and the ability to install untrusted applications on the target device, making it a local privilege escalation threat rather than a remote attack. This aligns with ATT&CK technique T1068 which covers "Local Privilege Escalation" and specifically addresses methods that allow adversaries to gain elevated privileges through weaknesses in system controls. Security researchers have noted that the vulnerability could potentially be chained with other exploits to achieve more severe outcomes, such as complete device compromise or data exfiltration through telephony channels. Organizations and users should prioritize applying the May 2021 security patches to address this vulnerability, while network administrators should monitor for potential exploitation attempts through unusual telephony service modifications or unauthorized file system changes. The remediation approach focuses on proper access control implementation and ensuring that telephony processes maintain appropriate isolation from untrusted application environments.