An unauthenticated attacker can exploit an instruction-validation flaw in the OpenXiangShan NEMU RISC-V Vector decoder to trigger architectural state corruption and denial of service.

The vulnerability is an improper input validation flaw within the RISC-V Vector (RVV) instruction decoder. An unauthenticated attacker can provide crafted RISC-V binaries that cause the decoder to misinterpret invalid OP-V instructions as valid configuration instructions, bypassing illegal-instruction exceptions.

Successful exploitation leads to architectural state divergence and potential denial of service for applications relying on NEMU for sandboxing or instruction set emulation. This failure undermines the integrity of the execution environment, which could result in system instability or the compromise of security boundaries in environments where NEMU is used as a foundational emulation layer. The CVSS score of 7.5 reflects a high severity rating due to the ease of exploitation and the potential for significant disruption to systems utilizing this emulator.

Immediate Action: Update to version 2025.12.r2 or newer, where the RISC-V Vector decoder correctly validates the funct3 field for vset* instructions.

Proactive Monitoring: Monitor systems for unexpected application crashes or trap-handling errors that may indicate an attempt to inject malicious RISC-V instruction sequences.

Compensating Controls: Ensure that any software running within the NEMU environment is strictly audited and sourced from trusted origins to prevent the execution of malicious binary code.

Public Exploit Available: No

Given the potential for denial of service and state corruption, organizations using NEMU for emulation or sandboxing must prioritize updating to the patched version. The ability to manipulate architectural state through crafted binaries poses a significant risk to the integrity of sandboxed environments, making timely remediation essential to maintain system stability.