CVE-2026-21128 in Checkout
Summary
by MITRE • 10/12/2026
Improper input validation in CreditCardRegisterActivity of Samsung Checkout prior to version 5.1.03.1 allows local attackers to launch arbitrary activity with Samsung Checkout privileges.
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Analysis
by VulDB Data Team • 10/12/2026
The vulnerability identified as an improper input validation flaw within the CreditCardRegisterActivity component of Samsung Checkout versions prior to 5.1.03.1 represents a significant security risk rooted in insufficient sanitization and verification of user-supplied data. This specific activity is responsible for handling sensitive payment information, including credit card details, during the registration process. The core technical flaw lies in the application's failure to strictly validate inputs before processing them or passing them to underlying system components. In Android applications, activities are fundamental building blocks that represent a single screen with a user interface. When an activity is not properly secured against improper input handling, it can be exploited by local attackers who have access to the device environment. The lack of rigorous validation allows malicious actors to inject crafted data or manipulate intent extras in ways that bypass expected business logic constraints.
From a technical perspective, this vulnerability enables privilege escalation through component hijacking. By exploiting the weak input validation, an attacker can launch arbitrary activities within the Samsung Checkout application context. This means that code executed by these launched activities inherits the permissions and privileges associated with the Samsung Checkout app rather than those of the attacking application. In many cases, payment applications hold elevated permissions to access secure storage, handle sensitive cryptographic keys, or interact with banking APIs. If an attacker can trigger specific internal screens or functions without proper authorization checks, they may be able to bypass authentication mechanisms, extract stored credentials, or manipulate transaction data. This type of attack vector is particularly dangerous because it leverages the trust relationship between the operating system and a high-privilege application.
The operational impact of this vulnerability extends beyond simple data leakage. An attacker with local access on an infected device could potentially perform unauthorized financial transactions, steal stored payment methods, or gain deeper insights into user behavior by accessing protected screens within the checkout flow. This compromises the integrity of the entire mobile commerce ecosystem supported by Samsung Checkout. Users relying on this application for secure payments face a direct threat to their financial security and personal privacy. Furthermore, because the attack requires local access, it is often associated with malware installed via sideloading or compromised third-party app stores that can interact with other applications' components if exported activities are not properly protected by permission declarations or explicit intent filters.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) categories such as CWE-20: Improper Input Validation and CWE-915: Improper Modification of Functionally Important Control Parameters. The exploitation technique corresponds to ATT&CK Mobile Tactic TA0003: Persistence or TA0004: Privilege Escalation, specifically leveraging component hijacking techniques where an attacker manipulates the application's control flow by sending malicious intents to exported components. To mitigate this risk, developers must implement strict input validation routines that sanitize all data entering the CreditCardRegisterActivity before it is processed. Additionally, ensuring that sensitive activities are not exported or require specific signature-level permissions can prevent unauthorized applications from launching them. Regular security audits and static code analysis focused on intent handling and component exposure are essential to identifying such flaws early in the development lifecycle. Updating to version 5.1.03.1 or later is critical as it addresses these validation gaps, thereby restoring the integrity of the payment processing workflow and protecting user data from local exploitation attempts.