CVE-2026-21138 in Smart Switch
Summary
by MITRE • 10/12/2026
Insufficient verification of data authenticity in Smart Switch prior to version 3.7.73 allows physical attackers to install arbitrary applications.
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Analysis
by VulDB Data Team • 10/12/2026
The vulnerability identified as insufficient verification of data authenticity within the Smart Switch application, specifically affecting versions prior to 3.7.73, represents a critical failure in input validation and cryptographic integrity checks. This flaw stems from an architectural oversight where the application fails to adequately verify the digital signatures or authenticity tokens associated with incoming installation packages before proceeding with their execution. In modern mobile operating systems such as Android, applications are typically distributed through official channels that enforce strict signature verification to ensure that code has not been tampered with and originates from a trusted developer. However, in this specific implementation, the Smart Switch application does not strictly enforce these authenticity checks during the sideloading or manual installation process. This deficiency allows an attacker who possesses physical access to the device to bypass standard security controls designed to prevent unauthorized software execution. The absence of robust verification mechanisms means that any package presented to the installer is accepted based on superficial criteria rather than cryptographic proof of origin, effectively neutralizing a primary defense layer against malicious code injection.
From a technical perspective, this vulnerability aligns with CWE-345, which describes insufficient verification of data authenticity, and CWE-20, improper input validation. The core issue lies in the application's logic flow during the package parsing phase. When an installation request is initiated, whether through USB connection or local file selection, the software should validate the APK signature against a trusted keystore or verify that it matches the expected developer certificate associated with legitimate updates and applications from Samsung. Instead, the vulnerable version proceeds to extract and install the payload without confirming its integrity. This allows for the injection of malicious code disguised as legitimate application files. An attacker exploiting this flaw can craft a specially constructed APK file containing arbitrary payloads, such as spyware, keyloggers, or remote access trojans, and force the device to execute it by leveraging the trusted status often implicitly granted to applications installed via manufacturer-provided utilities like Smart Switch.
The operational impact of this vulnerability is severe for users who rely on physical security measures to protect their devices. Since the attack vector requires physical access, it primarily targets individuals whose devices are temporarily unattended or stolen. Once an attacker gains physical control and exploits this flaw, they can install arbitrary applications that operate with elevated privileges depending on the permissions granted during installation. These malicious applications can exfiltrate sensitive personal data including contacts, messages, photos, and authentication tokens for banking or social media accounts. Furthermore, because Smart Switch is a pre-installed system utility often perceived as trustworthy by users, victims may not suspect the source of newly installed apps, allowing malware to persist undetected for extended periods. This persistence enables long-term surveillance, financial theft, and potential use of the device in botnets or further lateral movement attacks within connected networks if network permissions are also compromised.
Mitigation strategies focus primarily on software updates and user awareness. The most effective remediation is to update the Smart Switch application to version 3.7.73 or later, where Samsung has implemented stricter verification protocols ensuring that only digitally signed packages from authorized sources are accepted for installation. Users should ensure their device operating system and all pre-installed manufacturer applications are kept up to date through official OTA updates or manual checks within settings. In environments where physical security cannot be guaranteed, such as corporate devices in shared spaces, additional controls like mobile device management solutions can restrict sideloading capabilities entirely regardless of application-level flaws. Additionally, users should enable Google Play Protect and third-party antivirus software that monitors for suspicious installation activities and unauthorized permission grants. Awareness training is also critical; users must understand that even applications from trusted vendors require verification if installed outside official app stores, and they should always verify the digital signature of an APK before proceeding with manual installations to prevent exploitation of such authenticity bypass vulnerabilities.