CVE-2026-21104 in Samsung
Summary
by MITRE • 09/09/2026
Heap-based buffer overflow in KnoxVault trustlet prior to SMR Sep-2026 Release 1 allows local privileged attackers to execute arbitrary code.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 09/09/2026
The vulnerability identified as a heap-based buffer overflow within the Samsung Knox Vault Trustlet represents a critical security flaw that compromises the integrity of hardware-backed secure execution environments. This specific defect exists in versions prior to the SMR September 2026 Release 1, affecting systems where the Trustlet processes data without adequate bounds checking on memory allocations. The heap is a region of computer memory used for dynamic allocation during program runtime, and when an application writes more data into this space than has been allocated, it overwrites adjacent memory structures. In the context of a Trustlet, which operates with elevated privileges within a secure enclave separate from the main operating system, such an overflow can corrupt critical control data including return addresses or function pointers stored in nearby heap metadata.
Local privileged attackers who have already gained access to the device through other means can exploit this flaw to achieve arbitrary code execution. By carefully crafting input that triggers the buffer overflow, an attacker can manipulate the memory layout of the Trustlet process. This manipulation allows for the injection and subsequent execution of malicious shellcode or the redirection of program flow to existing useful instruction sequences within the binary, commonly known as Return Oriented Programming techniques. Because Knox Vault handles sensitive operations such as key management, biometric data processing, and secure boot verification, compromising this component effectively neutralizes a primary defense layer designed to protect user privacy and device integrity against sophisticated threats.
The operational impact of this vulnerability is severe due to the elevated trust level assigned to the Trustlet environment. Successful exploitation grants an attacker full control over the execution context within Knox Vault, potentially allowing them to extract cryptographic keys, bypass authentication mechanisms, or modify secure storage contents without detection. This undermines the fundamental security model of Samsung Knox, which relies on hardware isolation to protect sensitive data even if the main operating system is compromised. The ability to execute arbitrary code in this space means that an attacker could establish persistent access within the secure element, making remediation difficult and potentially allowing for long-term surveillance or data exfiltration from applications that rely on Knox Vault services for security guarantees.
From a classification perspective, this vulnerability aligns with CWE-120 Buffer Copy without Checking Size of Input, which describes situations where software copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer. Furthermore, in terms of attack tactics and techniques as defined by MITRE ATT&CK, this flaw facilitates privilege escalation within a specific process context and enables code injection or execution via memory corruption exploits such as heap spraying or overflow-based control flow hijacking. These classifications highlight the technical nature of the defect and its potential for abuse in advanced persistent threat scenarios targeting mobile device security architectures.
Mitigation strategies primarily involve applying the vendor-provided software update that addresses this issue, specifically ensuring devices are updated to SMR September 2026 Release 1 or later where the heap allocation logic has been corrected with proper boundary checks and input validation mechanisms. For organizations managing fleets of these devices, it is imperative to enforce automated patch management policies to ensure timely deployment of security updates. Additionally, implementing runtime application self-protection measures can help detect anomalous memory access patterns indicative of exploitation attempts, although such defenses are secondary to the primary mitigation of applying the official firmware update that resolves the underlying code defect within the Trustlet binary.