CVE-2026-43400

Vulnerability

CVE-2026-43400 is a denial-of the Linux kernel's AMDGPU driver lacks an upper bound check on user-supplied values in the amdgpu_userq_signal_ioctl ioctl handler. The kernel's official fix notes that huge input values can lead to an out-of-memory (OOM) condition, effectively enabling a local denial of service by exhausting system memory [1].

The patch introduces a validation step that caps input values at AMDGPU_USERQ_MAX_HANDLES, a limit chosen to accommodate legitimate use cases while preventing excessive memory allocation].

Exploitation

An attacker with local access to a system using the affected AMDGPU driver can invoke the ioctl with a maliciously large argument. No special privileges beyond the ability to open and interact with the GPU device are required the attack surface is the standard device file interface exposed to user space.

The vulnerability is triggered pre-authentication for the specific resource the attacker simply calls the ioctl with a crafted value; no other form of authentication is bypassed.

Impact

Successful exploitation causes the kernel to attempt allocating an extremely large buffer, leading to OOM-killing processes or crashing the system. This is a classic denial-of-service vector comparable to previous kernel resource-exhaustion CVE entries.

Mitigation

The fix has been committed to the Linux kernel stable tree and is included in upstream releases starting with the commit referenced]. System administrators should apply the latest kernel updates from their distribution. No workaround is available other than restricting local access to the amdgpu device, which is impractical in most desktop scenarios.