CVE-2023-2598: Linux Kernel Privilege Escalation Flaw

CVE-2023-2598 Overview

A critical flaw was identified in the fixed buffer registration code for io_uring (io_sqe_buffer_register in io_uring/rsrc.c) in the Linux kernel. This vulnerability allows out-of-bounds access to physical memory beyond the end of the buffer, enabling full local privilege escalation. The io_uring subsystem, introduced in Linux kernel 5.1, provides a high-performance asynchronous I/O interface, and this flaw in its buffer registration mechanism can be exploited by local attackers to gain elevated privileges on affected systems.

Critical Impact

This vulnerability enables full local privilege escalation through out-of-bounds physical memory access, allowing attackers with local access to gain root-level control over affected Linux systems.

Affected Products

• Linux Kernel (multiple versions)
• NetApp HCI Baseboard Management Controller H300S
• NetApp HCI Baseboard Management Controller H410C
• NetApp HCI Baseboard Management Controller H410S
• NetApp HCI Baseboard Management Controller H500S
• NetApp HCI Baseboard Management Controller H700S

Discovery Timeline

• June 1, 2023 - CVE-2023-2598 published to NVD
• April 23, 2025 - Last updated in NVD database

Technical Details for CVE-2023-2598

Vulnerability Analysis

This vulnerability resides in the io_uring subsystem, specifically within the io_sqe_buffer_register function in io_uring/rsrc.c. The flaw is classified under CWE-416 (Use After Free) and CWE-787 (Out-of-Bounds Write), indicating both memory management issues and improper boundary checking in the buffer registration logic.

The io_uring interface allows applications to register fixed buffers for I/O operations to improve performance by avoiding repeated kernel-userspace memory mappings. However, due to improper validation in the buffer registration code, an attacker can cause the kernel to access physical memory locations beyond the intended buffer boundaries. This out-of-bounds access provides a powerful primitive for exploitation, as it allows reading and potentially modifying arbitrary physical memory contents.

Root Cause

The root cause lies in insufficient boundary validation within the io_sqe_buffer_register function when handling fixed buffer registrations. The code fails to properly validate buffer size parameters, allowing an attacker to craft malicious registration requests that reference memory regions outside the allocated buffer. This boundary checking failure creates a condition where the kernel trusts user-supplied size values without adequate verification, leading to physical memory access beyond legitimate boundaries.

Attack Vector

The attack requires local access to the target system with the ability to use io_uring system calls. An attacker would craft specially designed io_uring buffer registration requests that exploit the boundary validation flaw to access physical memory beyond the buffer limits.

The exploitation flow involves:

1. Creating an io_uring instance with specially crafted parameters
2. Registering fixed buffers with malicious size values
3. Triggering operations that cause the kernel to access memory beyond buffer boundaries
4. Leveraging the out-of-bounds access to read or write sensitive kernel memory
5. Achieving privilege escalation by manipulating kernel data structures

For detailed technical analysis, refer to the Openwall Security Mailing List discussion.

Detection Methods for CVE-2023-2598

Indicators of Compromise

• Unusual io_uring system call patterns from unprivileged processes
• Unexpected kernel memory access violations or warnings in system logs
• Signs of privilege escalation attempts following io_uring buffer registration operations
• Anomalous process behavior indicating elevated privileges gained without proper authentication

Detection Strategies

• Monitor system calls related to io_uring operations (io_uring_setup, io_uring_register) for suspicious patterns
• Deploy kernel auditing rules to track buffer registration activities in the io_uring subsystem
• Implement behavioral analysis to detect processes attempting unusual memory access patterns
• Use SentinelOne's real-time behavioral AI to identify exploitation attempts targeting kernel memory

Monitoring Recommendations

• Enable enhanced logging for kernel subsystems, particularly io_uring-related activities
• Monitor for unexpected privilege changes in running processes
• Deploy runtime kernel integrity monitoring to detect unauthorized memory modifications
• Configure alerts for dmesg entries indicating out-of-bounds or use-after-free conditions

How to Mitigate CVE-2023-2598

Immediate Actions Required

• Update affected Linux kernel versions to patched releases immediately
• Restrict io_uring access for unprivileged users if kernel updates cannot be applied immediately
• Review and audit systems for signs of prior exploitation
• Apply vendor-specific patches for NetApp HCI Baseboard Management Controller devices

Patch Information

Linux kernel developers have released patches addressing this vulnerability. System administrators should update to the latest stable kernel version available for their distribution. For NetApp HCI BMC devices, refer to the NetApp Security Advisory NTAP-20230703-0006 for specific patch information and firmware updates.

Workarounds

• Disable io_uring for unprivileged users by setting the kernel parameter kernel.io_uring_disabled=2
• Use seccomp filters to block io_uring system calls for non-essential applications
• Implement container isolation policies that restrict io_uring access
• Apply network segmentation to limit local access to critical systems running vulnerable kernels

# Disable io_uring for unprivileged users
echo 2 > /proc/sys/kernel/io_uring_disabled

# Make the setting persistent across reboots
echo "kernel.io_uring_disabled = 2" >> /etc/sysctl.conf
sysctl -p