CVE-2026-93178 in Linux
Summary
by MITRE • 09/18/2026
In the Linux kernel, the following vulnerability has been resolved:
drm/amdgpu/pm/powerplay: bounds-check voltage index in SMU7 lookup
vddInd and vddcInd fields from VBIOS-parsed tables are used to index into voltage lookup tables without a bounds check. Return -EINVAL when any index is out of range.
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Analysis
by VulDB Data Team • 09/18/2026
The vulnerability identified within the Linux kernel's AMDGPU driver, specifically in the powerplay subsystem for SMU7 hardware, represents a critical memory safety issue arising from insufficient input validation. The core technical flaw lies in the handling of voltage indices extracted directly from Video BIOS (VBIOS) parsed tables. These tables contain fields designated as vddInd and vddcInd, which are intended to point to specific entries within internal voltage lookup tables used by the driver to manage power states and clock frequencies. Under normal operational circumstances, these values should correspond to valid indices within the allocated arrays. However, the original implementation failed to perform any bounds checking on these user-controlled or hardware-provided inputs before using them as array indexes. This lack of validation creates a direct path for out-of-bounds memory access if the VBIOS data is malformed, corrupted, or maliciously crafted by an attacker with physical access to the system firmware or through other means that allow modification of BIOS tables.
From a security architecture perspective, this flaw aligns closely with CWE-125, which describes Out-of-Bounds Read vulnerabilities. When the driver attempts to read from these lookup tables using unchecked indices, it may retrieve sensitive kernel memory contents located adjacent to the intended array boundaries. In more severe scenarios where write operations are involved or if subsequent logic relies on this corrupted data for control flow decisions, the risk escalates to CWE-787, an Out-of-Bounds Write vulnerability. The absence of boundary checks violates fundamental principles of defensive programming and secure coding standards that mandate strict validation of all external inputs before they influence internal state or memory access patterns. This specific implementation detail highlights a common pitfall in low-level system drivers where performance optimization sometimes leads to the omission of safety checks, assuming hardware data is always well-formed, which is an unsafe assumption in modern threat models involving firmware tampering.
The operational impact of this vulnerability extends beyond simple information disclosure. An attacker who can manipulate VBIOS tables or exploit a pre-existing condition that causes malformed parsing could potentially trigger arbitrary code execution by leveraging the out-of-bounds access to overwrite critical kernel structures, such as function pointers or control flow integrity metadata. Even if limited to read-only impacts, the leakage of kernel memory addresses facilitates further exploitation steps like Return-Oriented Programming (ROP) attacks by revealing base addresses of loaded modules and the kernel itself. This significantly lowers the barrier for privilege escalation from a local unprivileged user to root level access. In terms of threat modeling, this vulnerability can be mapped to MITRE ATT&CK techniques related to initial access via firmware manipulation or exploitation of driver vulnerabilities for lateral movement and persistence within the operating system environment.
To mitigate this risk, the resolution involves implementing strict bounds checking logic before any array indexing operation occurs. The fix ensures that both vddInd and vddcInd are validated against the maximum valid index size of their respective lookup tables. If either value exceeds these limits or falls below zero, the function immediately returns an error code, specifically -EINVAL, indicating invalid argument. This defensive measure prevents the kernel from accessing unauthorized memory regions and forces the power management subsystem to handle the anomaly gracefully rather than proceeding with corrupted data. System administrators should ensure that their systems are updated with patches containing this fix to close the gap in input validation within the AMDGPU driver. Furthermore, organizations relying on Linux-based infrastructure for critical workloads involving GPU acceleration should verify compliance with secure coding standards such as MISRA C or CERT C, which emphasize rigorous bounds checking and validation of all external data sources to prevent similar memory safety violations in future development cycles.