CVE-2023-2176: Linux Kernel Privilege Escalation Flaw

CVE-2023-2176 Overview

A vulnerability was discovered in the Linux Kernel's RDMA (Remote Direct Memory Access) subsystem, specifically in the compare_netdev_and_ip function located in drivers/infiniband/core/cma.c. This Out-of-Bounds Read vulnerability results from improper cleanup procedures, enabling a local attacker with low privileges to read memory outside the intended boundaries. Successful exploitation can lead to system crashes (denial of service) or potentially privilege escalation on affected systems.

Critical Impact

Local attackers can exploit improper cleanup in the RDMA subsystem to trigger out-of-bounds memory reads, potentially crashing the system or escalating privileges to gain elevated access.

Affected Products

• Linux Kernel (all versions with vulnerable RDMA subsystem)
• Systems utilizing InfiniBand/RDMA functionality
• Enterprise Linux distributions with affected kernel versions

Discovery Timeline

• April 20, 2023 - CVE-2023-2176 published to NVD
• May 5, 2025 - Last updated in NVD database

Technical Details for CVE-2023-2176

Vulnerability Analysis

This vulnerability exists within the RDMA Connection Manager (CMA) component of the Linux Kernel. The compare_netdev_and_ip function in drivers/infiniband/core/cma.c fails to properly clean up resources under certain conditions, leaving memory in an inconsistent state. This improper cleanup creates conditions where subsequent memory access operations can read beyond allocated buffer boundaries.

The vulnerability requires local access to the system and low privileges to exploit. No user interaction is necessary for exploitation, and the scope remains unchanged (meaning the vulnerable component and impacted component are the same). Successful exploitation can result in high impact to confidentiality, integrity, and availability of the affected system.

The RDMA subsystem is commonly used in high-performance computing environments and data centers for low-latency network communication. Organizations running InfiniBand hardware or using RDMA over Converged Ethernet (RoCE) should prioritize assessment of this vulnerability.

Root Cause

The root cause of CVE-2023-2176 lies in improper resource cleanup within the compare_netdev_and_ip function. When comparing network device and IP address information during RDMA connection management operations, the function fails to properly manage memory boundaries or clean up intermediate state. This creates a condition where memory reads can extend beyond the allocated buffer, potentially exposing sensitive kernel memory contents or corrupting kernel data structures.

Attack Vector

The attack vector for this vulnerability is local, requiring an attacker to have authenticated access to the affected system with at least low-level privileges. The attacker must be able to interact with the RDMA subsystem, typically through system calls or by manipulating RDMA-related interfaces.

The exploitation process involves triggering the vulnerable code path in the RDMA Connection Manager, causing the improper cleanup condition to occur. Once triggered, the out-of-bounds read can be leveraged to:

1. Information Disclosure: Read sensitive kernel memory that may contain credentials, cryptographic keys, or other security-relevant data
2. Denial of Service: Cause kernel panic or system instability by accessing invalid memory regions
3. Privilege Escalation: In certain scenarios, leverage the memory corruption to elevate privileges

The vulnerability's characteristics make it particularly relevant for multi-tenant environments, virtualized systems, and any scenario where local users should be restricted from accessing kernel-level resources.

Detection Methods for CVE-2023-2176

Indicators of Compromise

• Unexpected kernel panic events or system crashes related to RDMA/InfiniBand operations
• Abnormal memory access patterns in kernel logs associated with cma.c or InfiniBand drivers
• Unusual privilege escalation attempts following RDMA subsystem interactions
• Kernel oops messages referencing compare_netdev_and_ip or RDMA connection manager functions

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for out-of-bounds access warnings or RDMA-related errors
• Deploy kernel-level monitoring tools to detect anomalous memory access patterns in the InfiniBand subsystem
• Implement file integrity monitoring on kernel modules related to RDMA (ib_core, rdma_cm)
• Use security tools capable of detecting privilege escalation attempts following kernel vulnerability exploitation

Monitoring Recommendations

• Enable kernel auditing for system calls related to RDMA operations
• Configure alerting for kernel panic events and unexpected system reboots
• Monitor for users or processes unexpectedly interacting with InfiniBand/RDMA interfaces
• Implement endpoint detection and response (EDR) solutions that can detect kernel-level exploitation attempts

How to Mitigate CVE-2023-2176

Immediate Actions Required

• Update the Linux Kernel to a patched version that addresses the vulnerability in drivers/infiniband/core/cma.c
• Review system access controls to limit which users can interact with RDMA subsystems
• Audit systems to identify which hosts have InfiniBand/RDMA functionality enabled
• Consider disabling RDMA functionality on systems where it is not required until patches can be applied

Patch Information

Linux kernel maintainers have addressed this vulnerability in updated kernel releases. Organizations should consult the Linux RDMA mailing list announcement for specific patch details. Additionally, NetApp Security Advisory NTAP-20230609-0005 provides guidance for NetApp product users.

Administrators should update to the latest stable kernel version provided by their Linux distribution. Major enterprise distributions including Red Hat Enterprise Linux, Ubuntu, SUSE, and Debian have released security updates addressing this vulnerability.

Workarounds

• Disable InfiniBand/RDMA kernel modules if not required for business operations using modprobe -r ib_core rdma_cm
• Restrict access to RDMA devices by configuring appropriate file permissions on /dev/infiniband/ devices
• Implement mandatory access control policies (SELinux, AppArmor) to limit RDMA subsystem access to authorized applications only
• Segment high-value systems away from untrusted users who might attempt local exploitation

# Configuration example - Disable RDMA modules if not needed
# Add to /etc/modprobe.d/rdma-blacklist.conf
blacklist ib_core
blacklist rdma_cm
blacklist ib_cm
blacklist iw_cm

# Verify modules are not loaded
lsmod | grep -E "ib_core|rdma_cm"

# Restrict access to InfiniBand devices (if modules must remain loaded)
chmod 600 /dev/infiniband/*