CVE-2020-27484 in Forerunner 235
Summary
by MITRE • 11/17/2020
Garmin Forerunner 235 before 8.20 is affected by: Integer Overflow. The component is: ConnectIQ TVM. The attack vector is: To exploit the vulnerability, the attacker must upload a malicious ConnectIQ application to the ConnectIQ store. The ConnectIQ program interpreter fails to check for overflow when allocating the array for the NEWA instruction. This a constrained read/write primitive across the entire MAX32630 address space. A successful exploit would allow a ConnectIQ app store application to escape and perform activities outside the restricted application execution environment.
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Analysis
by VulDB Data Team • 12/08/2020
The vulnerability CVE-2020-27484 represents a critical integer overflow flaw in Garmin Forerunner 235 devices running firmware versions prior to 8.20. This vulnerability specifically affects the ConnectIQ TVM (Target Virtual Machine) component which serves as the execution environment for third-party applications on Garmin devices. The flaw manifests during the processing of the NEWA instruction within the ConnectIQ program interpreter, where insufficient input validation leads to improper array allocation calculations. The vulnerability falls under CWE-190, which specifically addresses integer overflow conditions, and aligns with ATT&CK technique T1059.007 for application layer execution through interpreter-based attacks. The attack vector requires an attacker to upload a malicious ConnectIQ application to the official ConnectIQ store, which then gets downloaded and executed on vulnerable devices.
The technical implementation of this vulnerability creates a constrained read/write primitive that spans the entire MAX32630 address space, which is the microcontroller architecture used in Garmin devices. When the NEWA instruction processes array allocation, the integer overflow causes the program to allocate insufficient memory, leading to memory corruption that can be exploited to gain unauthorized access to memory regions beyond the intended application boundaries. This memory corruption allows for arbitrary code execution within the device's operating environment, effectively breaking the sandboxing mechanism that normally isolates third-party applications from the core device functionality. The vulnerability demonstrates a classic case of insufficient bounds checking in memory management operations, where the lack of proper integer overflow detection creates a pathway for privilege escalation and system compromise.
The operational impact of this vulnerability extends beyond simple application-level exploitation to potentially compromise the entire device security model. An attacker who successfully uploads and executes a malicious application could gain access to sensitive device functions including GPS tracking data, user biometric information, and potentially communication protocols used for device synchronization. The vulnerability essentially allows for a complete bypass of the application sandbox, enabling malicious actors to perform activities outside the restricted execution environment that Garmin designed to protect users from unauthorized access. This represents a significant risk to user privacy and device integrity, particularly given the fitness tracking nature of these devices which often collect sensitive personal health data.
Mitigation strategies for CVE-2020-27484 require immediate firmware updates to version 8.20 or later, which addresses the integer overflow condition in the ConnectIQ TVM component. Users should also implement strict application review processes before installing third-party applications, particularly from untrusted sources. Organizations deploying Garmin devices for enterprise use should establish comprehensive patch management procedures and consider implementing network monitoring to detect anomalous application behavior. The vulnerability highlights the importance of proper input validation and bounds checking in embedded systems, particularly in IoT devices where device integrity directly impacts user safety and privacy. Security professionals should also consider implementing application whitelisting policies and regular security assessments to identify similar vulnerabilities in other embedded systems. This vulnerability serves as a reminder of the critical importance of secure coding practices in embedded environments where traditional security measures may not be sufficient to prevent exploitation of low-level memory management flaws.