EUVD-2025-21138CVSS VectorNVD
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionNVD
A vulnerability in the Software SMI handler (SwSmiInputValue 0x20) allows a local attacker to supply a crafted pointer (FuncBlock) through RBX and RCX register values. This pointer is passed unchecked into multiple flash management functions (ReadFlash, WriteFlash, EraseFlash, and GetFlashInfo) that dereference both the structure and its nested members, such as BufAddr. This enables arbitrary read/write access to System Management RAM (SMRAM), allowing an attacker to corrupt firmware memory, exfiltrate SMRAM content via flash, or install persistent implants.
AnalysisAI
CVE-2025-7028 is a critical privilege escalation vulnerability in Software SMI handlers that allows local authenticated attackers to achieve arbitrary read/write access to System Management RAM (SMRAM) through unchecked pointer dereference. The vulnerability affects firmware implementations using vulnerable SwSmiInputValue 0x20 handlers across multiple OEM platforms; attackers can corrupt firmware, exfiltrate SMRAM contents, or install persistent implants. With a CVSS score of 7.8 (High) and low attack complexity, this represents a significant firmware security risk, though exploitation requires local access and low privileges.
Technical ContextAI
This vulnerability exists in System Management Interrupt (SMI) handler firmware code, specifically in the Software SMI dispatch mechanism (SwSmiInputValue 0x20). The root cause is improper input validation (CWE-94: Improper Control of Generation of Code, or more broadly CWE-822: Untrusted Pointer Dereference). The vulnerable code path accepts user-controlled pointer values via x86-64 calling convention registers (RBX and RCX) that are directly dereferenced without validation in flash management functions (ReadFlash, WriteFlash, EraseFlash, GetFlashInfo). These functions perform unchecked reads/writes to the memory addresses and structures specified by the attacker-controlled pointers, including nested member access (e.g., BufAddr). SMRAM is a protected memory region accessible only during SMM (System Management Mode) execution, making this a privileged code path that can be invoked from user-mode through SMI calls. The vulnerability chains pointer injection with memory corruption capabilities.
RemediationAI
Remediation requires BIOS/UEFI firmware updates from OEM vendors: (1) Identify your system's current firmware version via BIOS setup utility or system tools (dmidecode on Linux, WMIC on Windows). (2) Visit the OEM's support website (motherboard manufacturer, laptop/server OEM) and download the latest BIOS/UEFI firmware release that includes patches for SMI handler validation. (3) Apply the patch according to OEM instructions (typically via firmware update utility). Patches should include input validation on RBX/RCX register values and pointer bounds checking before dereferencing in flash management functions. (4) As a temporary mitigation, restrict SMI handler invocation by disabling SMM features if not required (e.g., ACPI SMM, power management SMM), though this may disable system functionality. (5) Apply OS-level access controls to restrict user-mode SMI invocation on systems that support SMI call filtering. Vendor advisories and patch links should be obtained directly from OEM support pages; no specific patch links are provided in the source material.
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