CVE-2023-4272: Arm Bifrost GPU Information Disclosure Flaw

CVE-2023-4272 Overview

CVE-2023-4272 is an information disclosure vulnerability affecting multiple Arm Mali GPU kernel drivers. A local non-privileged user can exploit this vulnerability by performing GPU processing operations that expose sensitive data from previously freed memory. This use-after-free condition allows attackers to access memory contents that should have been cleared or reallocated, potentially revealing sensitive system information or data belonging to other users or processes.

Critical Impact

Local attackers can exploit GPU processing operations to access sensitive data from freed memory regions, potentially exposing confidential information including cryptographic keys, credentials, or private user data.

Affected Products

• Arm Bifrost GPU Kernel Driver (all versions prior to fix)
• Arm Valhall GPU Kernel Driver (all versions prior to fix)
• Arm Midgard GPU Kernel Driver (all versions prior to fix)
• Arm Mali GPU Kernel Driver version r41p0

Discovery Timeline

• 2023-11-07 - CVE-2023-4272 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-4272

Vulnerability Analysis

This vulnerability stems from improper memory handling within the Arm Mali GPU kernel drivers. When GPU memory is freed, the driver fails to properly sanitize or clear the memory contents before the memory region becomes available for reallocation. This creates a window where a local user can craft specific GPU processing operations to access stale data residing in these freed memory regions.

The attack requires local access with low privileges, meaning any authenticated user on a system with an affected Mali GPU can potentially exploit this vulnerability. The confidentiality impact is significant as the attacker can read sensitive memory contents without requiring any user interaction. However, the vulnerability does not allow modification of data (no integrity impact) or system disruption (no availability impact).

Root Cause

The root cause is classified under CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor). The Mali GPU kernel drivers inadequately handle memory lifecycle management, specifically failing to clear or sanitize GPU memory buffers after they are freed. This improper memory handling allows residual data to persist in freed memory regions that can subsequently be accessed through crafted GPU operations.

Attack Vector

The attack vector is local, requiring the attacker to have authenticated access to the target system. The exploitation process involves:

1. An attacker with local, non-privileged access identifies a system running a vulnerable Arm Mali GPU driver
2. The attacker submits specially crafted GPU processing jobs that target previously freed memory regions
3. The GPU driver processes these operations without proper memory validation
4. Data from freed memory buffers is returned to the attacker, potentially containing sensitive information from other processes or kernel operations

The vulnerability is accessible through standard GPU APIs available to unprivileged users, making exploitation relatively straightforward once local access is obtained.

Detection Methods for CVE-2023-4272

Indicators of Compromise

• Unusual GPU memory access patterns or excessive GPU job submissions from non-graphics processes
• Anomalous memory allocation and deallocation sequences targeting GPU subsystems
• Unexpected processes querying or accessing GPU driver interfaces
• Memory analysis showing access to freed GPU memory regions

Detection Strategies

• Monitor GPU driver interactions for unusual memory access patterns using kernel-level auditing
• Implement process monitoring to detect applications making suspicious GPU API calls
• Deploy endpoint detection solutions capable of monitoring GPU driver behavior
• Audit local user activities involving GPU-intensive operations that don't match expected workloads

Monitoring Recommendations

• Enable verbose logging for Mali GPU kernel driver operations where available
• Monitor system logs for GPU-related errors or memory access violations
• Implement behavioral analysis to detect exploitation attempts targeting GPU subsystems
• Use SentinelOne's kernel-level visibility to track GPU driver interactions and memory operations

How to Mitigate CVE-2023-4272

Immediate Actions Required

• Identify all systems running affected Arm Mali GPU kernel drivers (Bifrost, Valhall, Midgard, or Mali version r41p0)
• Review the Arm Security Center Mali GPU Driver Vulnerabilities advisory for the latest patches
• Prioritize patching systems accessible to multiple local users
• Restrict local access to affected systems while patches are being deployed

Patch Information

Arm has released security updates addressing this vulnerability. System administrators should consult the official Arm Security Center for specific patch versions and update instructions for their affected GPU drivers. The patch addresses the improper memory handling by ensuring freed GPU memory is properly sanitized before being made available for reallocation.

Workarounds

• Restrict local user access to systems with affected Mali GPU drivers where possible
• Implement strict user access controls to limit the number of users with local authentication
• Consider disabling non-essential GPU functionality on sensitive systems until patches can be applied
• Monitor for suspicious GPU-related activity as an interim detection measure

# Check for affected Mali GPU driver versions
lsmod | grep mali
cat /sys/module/mali_kbase/version 2>/dev/null || echo "Version info not available"
# Review loaded GPU kernel modules
modinfo mali_kbase 2>/dev/null | grep -E "version|filename"