CVE-2023-6241: Arm 5th Gen GPU Driver Use-After-Free Flaw

CVE-2023-6241 Overview

CVE-2023-6241 is a Use After Free vulnerability affecting multiple ARM Mali GPU kernel drivers, including Midgard, Bifrost, Valhall, and the 5th Gen GPU Architecture Kernel Driver. This vulnerability allows a local non-privileged user to exploit a software race condition to perform improper memory processing operations. When a system's memory is carefully prepared by an attacker, this can trigger a use-after-free condition, potentially leading to privilege escalation, arbitrary code execution, or system compromise.

Critical Impact

Local non-privileged users can exploit this race condition to achieve improper memory processing operations, potentially leading to privilege escalation or code execution at kernel level on affected ARM Mali GPU devices.

Affected Products

• Arm Midgard GPU Kernel Driver: from r13p0 through r32p0
• Arm Bifrost GPU Kernel Driver: from r11p0 through r25p0
• Arm Valhall GPU Kernel Driver: from r19p0 through r25p0, from r29p0 through r46p0
• Arm 5th Gen GPU Architecture Kernel Driver: from r41p0 through r46p0

Discovery Timeline

• 2024-03-04 - CVE-2023-6241 published to NVD
• 2025-03-13 - Last updated in NVD database

Technical Details for CVE-2023-6241

Vulnerability Analysis

This Use After Free vulnerability (CWE-416) exists in ARM's Mali GPU kernel drivers across multiple product generations. The flaw stems from a race condition in memory management operations that can be triggered by a local user with low privileges. When exploited, the vulnerability allows an attacker to manipulate memory in ways that can lead to reading or writing to freed memory regions.

The attack requires local access to the system and involves complex timing to exploit the race condition successfully. However, if successful, an attacker could achieve high impact across confidentiality, integrity, and availability of the affected system, potentially gaining elevated privileges or executing arbitrary code at the kernel level.

Root Cause

The root cause of CVE-2023-6241 is a race condition in the GPU kernel driver's memory management subsystem. The driver fails to properly synchronize access to memory objects, allowing a scenario where memory can be freed while still being referenced. This time-of-check time-of-use (TOCTOU) style vulnerability occurs when:

1. A memory object is allocated and referenced by the GPU driver
2. A race condition allows concurrent operations to free the memory
3. The original reference continues to access the now-freed memory region
4. The attacker can manipulate the contents of the freed memory to control execution flow

Attack Vector

The attack vector is local, requiring an attacker to have user-level access to a system with an affected ARM Mali GPU. The exploitation process involves:

1. Memory Preparation: The attacker carefully prepares system memory by allocating and arranging memory objects in a predictable pattern
2. Race Condition Trigger: The attacker initiates concurrent GPU operations designed to trigger the race condition between memory allocation and deallocation
3. Use-After-Free Exploitation: Once the race is won, the attacker can access freed memory, potentially replacing it with malicious data structures that redirect code execution

The vulnerability mechanism involves timing-sensitive operations in the GPU driver's memory handling routines. An attacker must craft specific GPU operations that can trigger the race window where memory is freed but still accessible through a dangling reference. For detailed technical information, refer to the ARM Security Center Advisory.

Detection Methods for CVE-2023-6241

Indicators of Compromise

• Unusual GPU driver crashes or kernel panics related to Mali GPU operations
• Abnormal memory allocation patterns in GPU kernel driver logs
• Evidence of privilege escalation attempts from unprivileged user accounts on ARM-based devices
• Suspicious processes interacting with GPU device files (/dev/mali*)

Detection Strategies

• Monitor kernel logs for Mali GPU driver error messages indicating memory corruption or use-after-free conditions
• Implement runtime kernel integrity checking to detect memory corruption
• Deploy endpoint detection solutions capable of identifying exploitation attempts targeting GPU drivers
• Enable kernel address space layout randomization (KASLR) to increase exploitation complexity

Monitoring Recommendations

• Monitor system calls to GPU driver device interfaces for anomalous patterns
• Track process behavior on ARM-based systems for unexpected privilege level changes
• Implement anomaly detection for GPU memory allocation and deallocation operations
• Review kernel crash dumps for signatures matching use-after-free exploitation

How to Mitigate CVE-2023-6241

Immediate Actions Required

• Update affected ARM Mali GPU kernel drivers to the latest patched versions immediately
• Restrict local user access to systems with vulnerable GPU drivers where possible
• Enable kernel security features such as KASLR and stack canaries to increase exploitation difficulty
• Monitor affected systems for signs of exploitation attempts

Patch Information

ARM has released security patches addressing this vulnerability. System administrators should update to driver versions beyond the affected ranges:

• Midgard GPU Kernel Driver: Update beyond r32p0
• Bifrost GPU Kernel Driver: Update beyond r25p0
• Valhall GPU Kernel Driver: Update beyond r46p0
• Arm 5th Gen GPU Architecture Kernel Driver: Update beyond r46p0

Consult the ARM Security Center for the latest security advisories and patch information. Device manufacturers may distribute these patches through firmware updates.

Workarounds

• Limit local user access to only trusted accounts on affected systems
• Implement mandatory access control (MAC) policies to restrict GPU device file access
• Consider disabling GPU acceleration for high-security environments until patches can be applied
• Deploy additional monitoring on systems that cannot be immediately patched

# Restrict access to Mali GPU device files as a temporary measure
chmod 600 /dev/mali*
chown root:root /dev/mali*

# Enable kernel address space layout randomization
echo 2 > /proc/sys/kernel/randomize_va_space