Description

Use After Free vulnerability in Arm Ltd Bifrost GPU Kernel Driver, Arm Ltd Valhall GPU Kernel Driver, Arm Ltd Arm 5th Gen GPU Architecture Kernel Driver allows a local non-privileged user process to perform valid GPU memory processing operations to access already freed memory. This issue affects Bifrost GPU Kernel Driver: from r41p0 through r49p5, from r50p0 through r51p0, from r54p1 through r54p2; Valhall GPU Kernel Driver: from r41p0 through r49p5, from r50p0 through r54p3, r55p0; Arm 5th Gen GPU Architecture Kernel Driver: from r41p0 through r49p5, from r50p0 through r54p3, r55p0.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "4.4",
  "pubDate": "2026-09-08T15:18:39.773Z",
  "pubdate": "2026-09-08T15:18:39.773Z",
  "executiveSummary": "A Use-After-Free (UAF) vulnerability has been identified within the kernel drivers for Arm Bifrost, Valhall, and 5th Gen GPU architectures. The vulnerability originates from improper memory management during GPU command processing, specifically concerning the lifecycle of memory objects shared between the kernel and user space.\nA local, non-privileged user process can exploit this flaw by manipulating GPU memory operations to trigger access to a memory region after it has been deallocated. Successful exploitation may lead to memory corruption, privilege escalation, or unauthorized access to sensitive kernel-mode memory structures.\nAffected products include the Bifrost, Valhall, and 5th Gen GPU Kernel Drivers across multiple release versions (r41p0 through r55p0 depending on architecture). The risk is categorized as high, as it allows local attackers to compromise kernel integrity without requiring prior authentication. Mitigation requires applying vendor-supplied driver updates to ensure proper synchronization and memory object reference counting.",
  "technicalDetails": "The vulnerability is a Use-After-Free (UAF) condition residing in the GPU kernel driver's memory management subsystem. This flaw occurs because the driver fails to correctly track the reference count or synchronization state of GPU memory allocations when they are freed during active operations. When a user-space process initiates specific, valid GPU memory processing requests, the driver prematurely deallocates the underlying memory buffer while the GPU hardware or subsequent kernel logic still maintains a reference or pending operation for that buffer.\nThe attack flow begins when a local, non-privileged process initiates a memory allocation and subsequent processing request via the GPU driver's interface. By triggering an error state or a specific sequence of ioctl calls, the attacker can force the kernel to free the memory object while the kernel component expects the object to remain valid for further processing. The kernel driver continues to use the dangling pointer associated with the freed object for subsequent reads, writes, or execution flows.\nBecause the memory is freed but remains referenced by kernel-mode pointers, an attacker can perform 'heap grooming' or 'heap spraying' to reallocate the freed memory block with attacker-controlled data. Once the memory is reallocated, the vulnerable driver component unknowingly interacts with the malicious payload stored within that memory region. This transition from a UAF to a controlled overwrite allows the attacker to hijack kernel execution flow or extract sensitive information stored in adjacent kernel memory structures.\nThe vulnerability affects the following driver branches: Bifrost GPU Kernel Driver (r41p0 through r49p5, r50p0 through r51p0, r54p1 through r54p2), Valhall GPU Kernel Driver (r41p0 through r49p5, r50p0 through r54p3, r55p0), and Arm 5th Gen GPU Architecture Kernel Driver (r41p0 through r49p5, r50p0 through r54p3, r55p0). Exploitation requires local access on the target device. No authentication is necessary, as the driver interface is exposed to unprivileged processes. The primary impact involves potential arbitrary code execution within the kernel context, leading to full system compromise, bypassing standard security boundaries imposed by the kernel's memory management unit."
}