CVE-2026-21157 in Bixby
Summary
by MITRE • 10/29/2026
Improper input validation in Bixby prior to version 4.0.85.6 allows privileged local attackers to launch arbitrary activity.
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Analysis
by VulDB Data Team • 10/29/2026
The vulnerability identified as an improper input validation flaw within Samsung's Bixby voice assistant software, specifically affecting versions prior to 4.0.85.6, represents a significant security risk for devices running the affected operating system build. This defect stems from insufficient sanitization and verification of user-supplied data before it is processed by the application logic. In typical secure design principles, input validation serves as the first line of defense against malicious payloads, ensuring that only expected formats and values are accepted. When this mechanism fails, particularly in a privileged context such as Bixby which often operates with elevated permissions to access system resources like contacts, location data, and installed applications, it creates an avenue for exploitation by local actors who have already gained some level of access to the device.
The core technical flaw involves the application's failure to properly validate inputs that trigger specific activities or intents within the Android framework. In mobile operating systems, components such as Activities are fundamental building blocks used to perform single actions. If a malicious actor can supply crafted input strings that bypass validation checks, they may be able to launch arbitrary activities without proper authorization or user consent. This capability effectively allows an attacker to manipulate the application's behavior in unintended ways, potentially leading to unauthorized access to sensitive data or execution of code within the security context of the Bixby service. The severity is amplified by the fact that the attack requires local privileges, meaning the threat actor must already have some form of access to the device, which could be achieved through physical access if lock screen protections are bypassed or via a previously compromised application with sufficient permissions.
From an operational impact perspective, this vulnerability enables privilege escalation and unauthorized control over system functions. An attacker leveraging this flaw could potentially exfiltrate personal information stored within Bixby's scope, such as voice history, contact details, or calendar events. Furthermore, the ability to launch arbitrary activities might be chained with other vulnerabilities to achieve more severe outcomes, including remote code execution if combined with additional flaws in underlying system services. The impact extends beyond data privacy; it compromises the integrity of the user experience and trust in the device's security model. Users relying on Bixby for automation or smart home control could find their devices manipulated to perform actions they did not authorize, such as making calls, sending messages, or altering settings.
This vulnerability aligns with Common Weakness Enumeration (CWE) category CWE-20: Improper Input Validation, which describes cases where software does not properly validate input that can affect the control flow of a program. Additionally, it relates to ATT&CK techniques involving Local Privilege Escalation and potentially Command and Scripting Interpreter if the launched activities involve executing scripts or commands through system interfaces. The exploitation path typically falls under lateral movement within a compromised device environment, where an attacker moves from a lower-privileged context to one with higher privileges by abusing trusted applications like Bixby.
Mitigation strategies primarily focus on patch management and configuration hardening. Users should immediately update their devices to version 4.0.85.6 or later of the Bixby application, as this release contains fixes for the input validation logic that prevent the exploitation of this flaw. For enterprise environments managing fleets of Samsung devices, ensuring consistent deployment of security patches through Mobile Device Management (MDM) solutions is critical. Additionally, implementing strict app permission policies can limit the potential impact if a vulnerability were to be exploited in other applications by restricting what data and system functions are accessible to third-party apps. Regular audits of installed applications and removal of unused services further reduce the attack surface available to local attackers seeking to leverage such vulnerabilities for privilege escalation or data theft.