CVE-2025-45006 in RISC-V Processor
Summary
by MITRE • 07/01/2025
Improper mstatus.SUM bit retention (non-zero) in Open-Source RISC-V Processor commit f517abb violates privileged spec constraints, enabling potential physical memory access attacks.
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Analysis
by VulDB Data Team • 07/02/2025
The vulnerability described in CVE-2025-45006 represents a critical flaw in the privilege level handling of a RISC-V processor implementation that has significant implications for system security and memory protection mechanisms. This issue manifests in the improper retention of the mstatus.SUM bit during processor operation, specifically when this bit maintains a non-zero value in violation of the RISC-V privileged specification requirements. The mstatus register serves as a fundamental control and status register within the RISC-V architecture that governs processor privilege levels and memory access permissions, making this particular flaw particularly dangerous for systems relying on proper privilege separation.
The technical implementation flaw occurs within the processor's privileged mode handling logic where the SUM bit, which controls supervisor-level memory access permissions, fails to properly maintain its expected zero value during certain processor states. According to the RISC-V Privileged Architecture specification, the SUM bit in the mstatus register should be zero when the processor is not in supervisor mode, as this bit enables supervisor-level access to user-mode memory regions. When this bit retains a non-zero value, it effectively allows the processor to access memory regions that should be restricted to user mode only, creating a potential pathway for privilege escalation attacks.
This vulnerability creates substantial operational impact by enabling potential physical memory access attacks that could bypass fundamental memory protection mechanisms. Attackers exploiting this flaw could potentially access memory regions that should be isolated between user and supervisor modes, leading to unauthorized data access, privilege escalation, and potential system compromise. The vulnerability affects systems using the specific Open-Source RISC-V processor implementation referenced in commit f517abb, which may be deployed in various embedded systems, IoT devices, and other applications where RISC-V processors are utilized for their open-source nature and cost-effectiveness.
The security implications extend beyond simple memory access violations as this flaw could enable attackers to execute code in supervisor mode using user-mode privileges, potentially leading to complete system compromise. This type of vulnerability aligns with CWE-284, which addresses improper privilege management in software systems, and could be categorized under ATT&CK technique T1068, which involves exploiting local privilege escalation vulnerabilities. The improper handling of the SUM bit creates a direct pathway for attackers to bypass memory protection mechanisms that are fundamental to maintaining system integrity and preventing unauthorized access to sensitive data and system resources.
Mitigation strategies for this vulnerability require immediate updates to the processor firmware or software implementation to ensure proper handling of the mstatus.SUM bit according to the privileged specification. System administrators should implement firmware updates from the processor vendor or directly apply patches to the source code if using open-source implementations. Additionally, runtime monitoring systems should be enhanced to detect abnormal mstatus register states and potential privilege violations. The fix typically involves ensuring that the SUM bit is properly cleared during processor state transitions and that all privilege level changes properly enforce the memory access restrictions defined by the RISC-V specification. Organizations should also conduct thorough security assessments of systems using affected processor implementations to identify potential exploitation attempts and ensure proper privilege separation mechanisms are maintained throughout the system architecture.