CVE-2026-33957 in Exynos
Summary
by MITRE • 09/14/2026
An issue was discovered in CustOS Driver in Samsung Mobile Processor Exynos 1580. Requesting oversized shared memory from the custos_iwc device enables out-of-bounds read and write, potentially leading to memory corruption or information leakage.
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Analysis
by VulDB Data Team • 09/14/2026
The vulnerability identified within the CustOS Driver of the Samsung Exynos 1580 mobile processor represents a critical security flaw rooted in improper input validation during shared memory management operations. Specifically, the issue resides in the handling of requests directed at the custos_iwc device interface. When an application or process attempts to allocate or access shared memory regions that exceed predefined size limits, the driver fails to enforce strict boundary checks before proceeding with memory allocation and mapping procedures. This lack of rigorous validation allows for oversized buffers to be processed by the underlying kernel subsystems without appropriate sanitization or capacity verification, creating a fundamental breakdown in the isolation mechanisms designed to protect system resources from untrusted user-space applications.
From a technical perspective, this flaw manifests as both an out-of-bounds read and an out-of-bounds write vulnerability. The excessive memory requests bypass standard allocation constraints, leading to buffer overflows that extend beyond the allocated heap or stack boundaries into adjacent memory regions. An out-of-bounds write can corrupt critical kernel data structures, overwrite function pointers, or alter control flow mechanisms within the operating system environment. Simultaneously, an out-of-bounds read allows unauthorized access to sensitive information stored in neighboring memory locations, potentially exposing cryptographic keys, session tokens, or other privileged data that should remain inaccessible to lower-privilege processes. This dual nature of the vulnerability significantly increases its exploitability and potential impact on system integrity.
The operational impact of this vulnerability is severe, particularly given the role of CustOS as a secure execution environment within Samsung's mobile architecture. If successfully exploited, an attacker could achieve arbitrary code execution with kernel-level privileges by manipulating memory corruption to hijack control flow or escalate privileges from a sandboxed application context to the root level. Furthermore, the information leakage aspect poses significant privacy risks, enabling attackers to exfiltrate sensitive user data such as personal messages, financial credentials, and biometric templates stored in adjacent memory spaces. In the context of mobile devices where multiple applications run concurrently with varying trust levels, this vulnerability undermines the fundamental security model that relies on strict separation between trusted and untrusted execution domains.
This issue aligns closely with Common Weakness Enumeration (CWE) categories such as CWE-120 Buffer Copy without Checking Size of Input Classic Buffer Overflow and CWE-787 Out-of-bounds Write, which describe scenarios where input is not properly validated against buffer boundaries. Additionally, the exploitation path relates to ATT&CK techniques involving privilege escalation and data exfiltration from local applications, specifically mapping to behaviors associated with memory corruption attacks that bypass sandbox restrictions. The vulnerability highlights critical gaps in driver-level security controls within mobile SoCs, emphasizing the need for robust input validation mechanisms at every layer of the software stack.
Mitigation strategies must focus on implementing strict size verification checks before processing shared memory requests within the CustOS Driver. Developers should enforce maximum buffer limits and validate all incoming parameters against these constraints to prevent oversized allocations from reaching kernel-level handlers. Additionally, employing defensive programming techniques such as bounds checking libraries and address space layout randomization can reduce the likelihood of successful exploitation. Samsung must release a firmware update that patches this specific flaw in the custos_iwc device handling logic. Users should ensure their devices are updated with the latest security patches to mitigate exposure until official fixes are deployed across supported Exynos 1580-based products.