CVE-2018-4140 in iOS
Summary
by MITRE
An issue was discovered in certain Apple products. iOS before 11.3 is affected. The issue involves the "Telephony" component. It allows remote attackers to cause a denial of service (NULL pointer dereference and reboot) via a Class 0 SMS message.
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Analysis
by VulDB Data Team • 02/06/2021
The vulnerability identified as CVE-2018-4140 represents a critical security flaw within Apple's iOS telephony subsystem that affects versions prior to iOS 11.3. This issue resides within the Telephony component of the operating system, specifically targeting how the device processes incoming Class 0 SMS messages. The vulnerability manifests as a NULL pointer dereference condition that occurs when the telephony framework attempts to handle malformed or specially crafted Class 0 SMS messages. These particular SMS messages are characterized by their immediate delivery priority and are typically used for emergency alerts or time-sensitive communications, making them particularly dangerous when exploited in this manner.
The technical exploitation of this vulnerability occurs through the manipulation of Class 0 SMS message parameters that trigger an improper memory access pattern within the telephony processing code. When an affected iOS device receives such a message, the system attempts to dereference a NULL pointer during the message processing routine, causing an immediate system crash and subsequent automatic reboot of the device. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereference conditions, representing a fundamental memory management error that can lead to system instability and denial of service scenarios. The exploitation mechanism is particularly concerning because Class 0 SMS messages are designed to be delivered immediately and bypass normal messaging queues, meaning that a single malicious message can disrupt service on any affected device within range.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be weaponized to create widespread disruption across mobile networks and potentially target specific individuals or organizations. Attackers can leverage this vulnerability to repeatedly send malicious Class 0 SMS messages to affected devices, causing continuous reboots that render the device unusable until manual intervention occurs. This creates a vector for persistent denial of service attacks that can be executed remotely without requiring physical access to the target device or sophisticated network infrastructure. The vulnerability also demonstrates a lack of proper input validation within the telephony subsystem, as the system fails to adequately sanitize incoming SMS message parameters before processing them. From an operational security perspective, this issue highlights the importance of comprehensive testing for memory safety issues and proper error handling in mobile operating system components, particularly those handling real-time communication protocols.
Mitigation strategies for CVE-2018-4140 primarily involve upgrading affected iOS devices to version 11.3 or later, which includes patches that address the NULL pointer dereference condition in the telephony processing code. Apple's security update specifically modifies the message handling routines to include proper input validation and error checking before attempting to dereference pointers within the telephony framework. Network administrators and security professionals should also implement monitoring solutions to detect unusual patterns of Class 0 SMS message traffic that might indicate attempted exploitation of this vulnerability. Additionally, organizations should consider deploying mobile device management solutions that can enforce security policies and ensure timely patch deployment across enterprise device fleets. The vulnerability also underscores the importance of following ATT&CK framework concepts related to privilege escalation and denial of service, as this issue can be classified under techniques that leverage system-level memory corruption to achieve unauthorized system control and service disruption.