CVE-2025-56301 is a vulnerability identified in the Chipsalliance Rocket-Chip, specifically in the Control and Status Register (CSR) logic related to exception handling and privilege state transitions. The flaw arises from a problematic interaction between the exception handling mechanism and the MRET (Machine-mode Return from Exception) instruction execution. When an exception is triggered during the execution of the MRET instruction, the CSR logic erroneously allows both the exception handling and the exception return logic to activate simultaneously. This leads to conflicting updates to the control and status registers, resulting in faulty trap behavior. Specifically, if the MRET instruction is executed in machine mode without the processor being in an exception state, it can trigger an Instruction Access Fault. This fault can corrupt the exception handling flow and privilege state transitions, potentially allowing attackers to manipulate the processor's control flow or privilege levels. The vulnerability is rooted in the Rocket-Chip commit f517abbf41abb65cea37421d3559f9739efd00a9, with no specific affected versions enumerated. No known exploits are reported in the wild, and no patches have been linked yet. The vulnerability was reserved in August 2025 and published in September 2025, with no CVSS score assigned at the time of publication.

For European organizations, the impact of CVE-2025-56301 depends largely on the deployment of systems utilizing the Chipsalliance Rocket-Chip architecture. This chip design is commonly used in RISC-V based processors, which are increasingly adopted in embedded systems, IoT devices, and specialized computing environments. The vulnerability could allow attackers to corrupt exception handling and privilege states, potentially enabling privilege escalation or denial of service through faulty trap behavior. This could compromise the confidentiality, integrity, and availability of affected systems. In critical infrastructure sectors such as telecommunications, manufacturing automation, and transportation—where embedded RISC-V processors may be deployed—this vulnerability could disrupt operations or enable further attacks. Given the low maturity of exploit development and no known active exploitation, the immediate risk is moderate; however, the potential for privilege escalation and control flow corruption makes this a significant concern for sensitive or critical systems. European organizations relying on RISC-V based hardware for secure or safety-critical applications should consider this vulnerability a serious threat to system reliability and security.

Since no official patches or updates are currently available, European organizations should take proactive steps to mitigate the risk. First, conduct an inventory to identify any systems using the affected Rocket-Chip versions or RISC-V processors derived from this design. Engage with hardware vendors and suppliers to obtain information on firmware or microcode updates addressing this issue. Where possible, apply firmware updates or microcode patches once released. In the interim, implement strict access controls and monitoring on systems using these processors to detect anomalous behavior indicative of exploitation attempts. Employ hardware-level security features such as secure boot and trusted execution environments to limit the impact of corrupted exception handling. For embedded devices, consider isolating vulnerable components from critical network segments and applying network-level protections such as segmentation and intrusion detection. Additionally, review and harden exception handling and privilege management policies in software running on these processors to reduce attack surface. Collaborate with industry groups and participate in information sharing to stay informed about emerging patches and exploit techniques related to this vulnerability.