CVE-2025-51677 in OR1200
Summary
by MITRE • 07/17/2026
An issue was discovered in openRISC OR1200 commit 83ac6b. An output mismatch between the RTL and the netlist of the or1200 cpu output port can lead to unexpected behavior.
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Analysis
by VulDB Data Team • 07/17/2026
The vulnerability identified in the openRISC OR1200 processor represents a critical hardware design discrepancy that undermines the integrity of the CPU's output functionality. This issue manifests as an output mismatch between the Register Transfer Level (RTL) specification and the actual netlist implementation, creating a fundamental inconsistency in how the processor handles data output operations. The OR1200 is a 32-bit RISC microprocessor designed for embedded applications and FPGA implementations, making this discrepancy particularly concerning for security-sensitive environments where predictable hardware behavior is essential.
The technical flaw stems from a mismatch in the output port configuration between the high-level RTL description and the low-level netlist representation used for physical implementation. This discrepancy can cause data corruption or unexpected signal states when the processor attempts to drive output values onto its external interfaces. The mismatch may occur due to various factors including incorrect signal timing assumptions, improper handling of output enable signals, or inconsistencies in the logic synthesis process that translates RTL code into netlist format. Such mismatches are particularly dangerous because they can produce intermittent failures that are extremely difficult to diagnose and reproduce in testing environments.
The operational impact of this vulnerability extends beyond simple functional degradation to potentially compromise system security and reliability. When output signals do not behave as specified in the RTL design, it creates unpredictable behavior that could be exploited by malicious actors. The mismatch may result in data leakage through side-channel effects, incorrect interrupt handling, or failure to properly assert control signals that govern system operations. Attackers could potentially leverage this inconsistency to manipulate processor execution flow or extract sensitive information from the system's output channels. This vulnerability directly aligns with CWE-116 weakness classification related to improper encoding or representation of data and potentially maps to ATT&CK technique T1059 for command injection through malformed output handling.
Mitigation strategies should focus on comprehensive verification and validation of the RTL versus netlist consistency before deployment in security-critical applications. Hardware designers must implement rigorous formal verification processes including gate-level simulation, netlist-to-RTL comparison tools, and thorough testing of all output port behaviors under various operating conditions. The openRISC community should establish standardized validation procedures for hardware implementations that include automated checks for such mismatches. Additionally, system architects should consider implementing output monitoring mechanisms that can detect anomalous behavior patterns indicative of such hardware inconsistencies. Regular security assessments of embedded systems utilizing OR1200 processors should include verification of hardware implementation integrity to prevent exploitation of this class of vulnerability.