CVE-2023-2598: Linux Kernel Privilege Escalation Flaw

CVE-2023-2598 Overview

CVE-2023-2598 is a Linux kernel vulnerability in the io_uring subsystem's fixed buffer registration code. The flaw resides in the io_sqe_buffer_register function within io_uring/rsrc.c and allows out-of-bounds access to physical memory beyond the end of a registered buffer. A local, authenticated attacker can leverage this condition to achieve full local privilege escalation. The vulnerability affects the upstream Linux kernel and downstream products including NetApp HCI Baseboard Management Controller appliances. The issue is tracked under [CWE-416] (Use After Free) and [CWE-787] (Out-of-Bounds Write).

Critical Impact
Local users can escalate privileges to root by triggering out-of-bounds physical memory access through crafted io_uring buffer registrations.

Affected Products

Linux kernel (upstream, prior to fixed releases)
NetApp HCI Baseboard Management Controller (H300S, H410C, H410S, H500S, H700S)
Distributions shipping vulnerable io_uring implementations

Discovery Timeline

2023-05-08 - Public discussion on the Openwall oss-security mailing list
2023-06-01 - CVE-2023-2598 published to NVD
2023-07-03 - NetApp publishes advisory NTAP-20230703-0006
2025-04-23 - Last updated in NVD database

Technical Details for CVE-2023-2598

Vulnerability Analysis

The io_uring interface allows userspace to register fixed buffers for high-performance asynchronous I/O. The registration path stores buffer metadata used by subsequent read and write operations. In the vulnerable code path, the kernel computes buffer extents incorrectly, permitting I/O operations to access physical memory pages located beyond the buffer's intended boundary. Because io_uring operates at a low level with direct page references, the out-of-bounds access reaches physical memory rather than virtual addresses constrained by per-process page tables. An attacker with local access and the ability to issue io_uring syscalls can read and write to kernel-adjacent memory, corrupt privileged data structures, and gain root privileges.

Root Cause

The root cause is improper validation of buffer boundaries during fixed buffer registration in io_sqe_buffer_register within io_uring/rsrc.c. The function fails to enforce that all I/O accesses remain within the registered buffer's physical extents. This boundary error maps to [CWE-787] (Out-of-Bounds Write) and is associated with use-after-free conditions [CWE-416] when freed pages are accessed through stale buffer references.

Attack Vector

Exploitation requires local access with low privileges and no user interaction. The attacker calls io_uring_setup to create a ring, then uses IORING_REGISTER_BUFFERS to register a crafted buffer that triggers the boundary miscalculation. Subsequent submission queue entries direct I/O operations against the out-of-bounds memory, enabling arbitrary kernel memory read and write primitives. These primitives are commonly chained to overwrite credentials structures or function pointers to achieve root execution. Technical details are documented in the Openwall oss-security discussion and the follow-up Openwall thread.

// No verified public exploit code is referenced in the CVE data.
// See the Openwall oss-security discussions for technical analysis.

Detection Methods for CVE-2023-2598

Indicators of Compromise

Unexpected io_uring_setup and IORING_REGISTER_BUFFERS activity from non-privileged or unusual user contexts
Kernel oops, panics, or memory corruption traces referencing io_uring/rsrc.c or io_sqe_buffer_register
Sudden privilege transitions where a low-privileged process spawns a root shell or modifies /etc/passwd or /etc/shadow

Detection Strategies

Audit io_uring syscall usage with eBPF or auditd, flagging buffer registrations from processes that do not normally use asynchronous I/O
Monitor kernel ring buffer and dmesg output for crashes, KASAN reports, or warnings originating in io_uring code
Correlate process credential changes with prior io_uring syscall sequences to identify exploitation attempts

Monitoring Recommendations

Enable kernel address sanitizer (KASAN) in test environments to catch out-of-bounds access during validation
Collect telemetry on uid transitions and unexpected setuid(0) outcomes from non-root processes
Forward host telemetry to a centralized data lake for retrospective hunting against io_uring exploitation patterns

How to Mitigate CVE-2023-2598

Immediate Actions Required

Apply the upstream Linux kernel patch that corrects buffer boundary handling in io_sqe_buffer_register
Update vendor-shipped kernels from your distribution (Red Hat, SUSE, Ubuntu, Debian) to versions that incorporate the fix
For NetApp HCI BMC appliances, apply the firmware update referenced in NetApp advisory NTAP-20230703-0006

Patch Information

The Linux kernel maintainers corrected the boundary calculation in io_uring/rsrc.c. Distribution-specific advisories list the exact kernel package versions containing the fix. Administrators should consult their distribution's security tracker and apply the patched kernel, followed by a reboot. NetApp customers should follow the remediation steps in advisory NTAP-20230703-0006.

Workarounds

Disable io_uring for unprivileged users by setting kernel.io_uring_disabled=2 on kernels that support the sysctl (Linux 6.6 and later)
Restrict access to io_uring_setup via seccomp policies in container runtimes and systemd unit hardening
Limit local shell access on multi-tenant systems and enforce least-privilege account policies until patching is complete

bash

# Disable io_uring system-wide for unprivileged users (Linux 6.6+)
echo 'kernel.io_uring_disabled = 2' | sudo tee /etc/sysctl.d/99-io_uring.conf
sudo sysctl --system

# Verify the setting
sysctl kernel.io_uring_disabled

# For systemd services, add seccomp filter to block io_uring syscalls
# In the unit file:
# SystemCallFilter=~@io-uring