CVE-2026-31462: Linux Kernel Privilege Escalation Flaw

CVE-2026-31462 Overview

A race condition vulnerability has been identified in the Linux kernel's AMDGPU DRM (Direct Rendering Manager) driver related to PASID (Process Address Space ID) management. The vulnerability occurs when a PASID is immediately reused after a process exits, potentially causing interrupt handling issues when page faults from the previous process are still pending in the Interrupt Handler (IH) ring buffer.

Critical Impact

Systems with AMD GPUs may experience interrupt handling corruption and potential system instability when processes rapidly allocate and release PASIDs, allowing a new process to inherit pending page faults from a terminated process.

Affected Products

• Linux kernel with AMDGPU DRM driver
• Systems utilizing AMD GPUs with PASID-based address space management
• Linux distributions shipping affected kernel versions

Discovery Timeline

• April 22, 2026 - CVE-2026-31462 published to NVD
• April 23, 2026 - Last updated in NVD database

Technical Details for CVE-2026-31462

Vulnerability Analysis

This vulnerability represents a race condition in the AMDGPU driver's PASID allocation mechanism. PASIDs are used to identify process address spaces for GPU memory management and page fault handling. When a process exits and releases its PASID, the identifier may be immediately reassigned to a new process before pending interrupts from the previous process have been fully processed.

The core issue stems from the IH (Interrupt Handler) ring buffer potentially containing page fault entries associated with a PASID that has already been freed and reallocated. When a new process inherits this PASID, it may incorrectly handle interrupts that were destined for the previous process, leading to incorrect memory access patterns or system instability.

Root Cause

The root cause is the non-cyclic PASID allocation strategy previously used in the AMDGPU driver. Without cyclic allocation, freed PASIDs could be immediately reassigned to new processes. This created a window where pending page faults in the IH ring buffer, still referencing the old PASID, would be misrouted to the new process that had been assigned the same identifier.

The fix implements an IDR (ID Radix tree) cyclic allocator for PASID management, similar to the approach used by the kernel for process IDs (PIDs). This ensures that a recently freed PASID is not immediately reused, providing sufficient time for pending interrupts to be processed before the identifier is recycled.

Attack Vector

The attack vector for this vulnerability involves local access to a system with an AMD GPU. An attacker or faulty application could potentially trigger this condition through:

1. Rapidly creating and terminating GPU-utilizing processes to cause PASID churn
2. Timing the creation of a new process to inherit a PASID with pending page faults
3. Exploiting the misrouted interrupts to cause system instability or potentially access memory regions intended for the previous process

The vulnerability requires local access and the ability to execute GPU workloads, making exploitation dependent on local privileges and hardware configuration.

Detection Methods for CVE-2026-31462

Indicators of Compromise

• Unexpected GPU page fault errors in kernel logs associated with processes that should not have GPU memory mappings
• System instability or crashes occurring during periods of high GPU process turnover
• Kernel messages indicating PASID-related interrupt handling errors in the AMDGPU driver
• Anomalous behavior in GPU-accelerated applications following rapid process termination

Detection Strategies

• Monitor kernel logs (dmesg) for AMDGPU driver warnings or errors related to PASID or page fault handling
• Implement system monitoring for unexpected GPU memory access patterns
• Track process creation and termination rates for GPU-utilizing applications
• Enable kernel tracing for DRM subsystem events to identify PASID allocation anomalies

Monitoring Recommendations

• Deploy SentinelOne Singularity Platform for real-time kernel-level monitoring and anomaly detection
• Configure alerts for AMDGPU driver error messages in system logs
• Monitor for unusual patterns of GPU process creation and termination
• Implement kernel integrity monitoring to detect exploitation attempts

How to Mitigate CVE-2026-31462

Immediate Actions Required

• Update the Linux kernel to a patched version containing the PASID cyclic allocator fix
• Review systems with AMD GPUs for signs of exploitation or instability
• Consider temporarily reducing GPU workload intensity on affected systems until patches are applied
• Monitor system stability and kernel logs for AMDGPU-related errors

Patch Information

The vulnerability has been resolved in the Linux kernel through commits that implement IDR cyclic allocation for PASID management. Multiple patches have been backported to stable kernel branches:

• Kernel Git Commit 14b81abe
• Kernel Git Commit 51ccaf0e
• Kernel Git Commit 9e5ebfe9
• Kernel Git Commit c0b38828

The fix modifies the PASID allocator to use idr_alloc_cyclic() instead of immediate reuse, ensuring that freed PASIDs are not reassigned until the allocator cycles through other available identifiers.

Workarounds

• Reduce the frequency of GPU process creation and termination where possible
• Implement application-level rate limiting for GPU workload spawning
• Consider using CPU-based alternatives for affected workloads until patches are applied
• Monitor and restart affected systems if instability is observed

# Check current kernel version for patch status
uname -r

# View AMDGPU driver messages for potential issues
dmesg | grep -i amdgpu | grep -iE "pasid|page.fault|interrupt"

# Update kernel to patched version (Debian/Ubuntu example)
sudo apt update && sudo apt upgrade linux-image-generic