CVE-2023-3268: Linux Kernel Privilege Escalation Flaw

CVE-2023-3268 Overview

An out-of-bounds (OOB) memory access vulnerability was discovered in the Linux kernel's relayfs implementation, specifically in the relay_file_read_start_pos function located in kernel/relay.c. This flaw allows a local attacker with low privileges to trigger an out-of-bounds read condition, potentially causing system crashes (denial of service) or leaking sensitive kernel internal information.

Critical Impact

Local attackers can exploit this vulnerability to crash the system or extract sensitive kernel memory contents, potentially revealing internal data structures, cryptographic keys, or other privileged information.

Affected Products

• Linux Kernel (multiple versions prior to 6.3.2)
• Debian Linux 10.0 (Buster)
• Debian Linux 11.0 (Bullseye)
• Debian Linux 12.0 (Bookworm)

Discovery Timeline

• June 16, 2023 - CVE-2023-3268 published to NVD
• March 11, 2025 - Last updated in NVD database

Technical Details for CVE-2023-3268

Vulnerability Analysis

The vulnerability exists in the Linux kernel's relay filesystem (relayfs), a high-speed data relay mechanism used for transferring large amounts of data from kernel space to user space. The flaw occurs in the relay_file_read_start_pos function within kernel/relay.c, which is responsible for calculating the starting position when reading relay buffer data.

The out-of-bounds read condition can be triggered when the function improperly calculates or validates buffer boundaries during read operations. This allows access to memory regions outside the intended relay buffer boundaries, which can expose kernel memory contents to an attacker or cause memory access violations leading to kernel panics.

The vulnerability requires local access and low privileges to exploit, but does not require user interaction. An attacker can potentially read sensitive kernel memory or cause a denial of service condition by triggering the vulnerable code path through relay filesystem operations.

Root Cause

The root cause is classified as CWE-125 (Out-of-bounds Read). The vulnerability stems from improper bounds checking in the relay_file_read_start_pos function when calculating the read position within relay buffers. The function fails to properly validate that the calculated start position falls within the allocated buffer boundaries, allowing reads beyond the intended memory region.

Attack Vector

The attack vector is local, requiring an attacker to have authenticated access to the target system with low privileges. The attacker can exploit this vulnerability by:

1. Gaining local access to a system running a vulnerable Linux kernel
2. Interacting with the relay filesystem interface
3. Triggering read operations that cause the relay_file_read_start_pos function to calculate an invalid buffer position
4. Observing the resulting kernel memory leak or system crash

The exploitation does not require user interaction and can be performed by any local user with access to the relay filesystem interface.

Detection Methods for CVE-2023-3268

Indicators of Compromise

• Unexpected kernel panics or system crashes related to relayfs operations
• Suspicious access patterns to relay filesystem interfaces by non-privileged users
• Kernel oops messages referencing relay_file_read_start_pos or kernel/relay.c
• Abnormal memory access patterns detected in kernel audit logs

Detection Strategies

• Monitor for kernel log messages indicating out-of-bounds memory access in relay-related functions
• Implement kernel integrity monitoring to detect exploitation attempts
• Use endpoint detection solutions to identify suspicious local process behavior interacting with relay interfaces
• Deploy SentinelOne agents configured to monitor kernel-level anomalies and memory access violations

Monitoring Recommendations

• Enable kernel audit logging for filesystem operations, particularly those involving relayfs
• Configure alerting for kernel panic events with stack traces containing relay functions
• Implement system call monitoring for relay-related operations from unexpected processes
• Deploy memory access monitoring tools to detect out-of-bounds read attempts

How to Mitigate CVE-2023-3268

Immediate Actions Required

• Update the Linux kernel to version 6.3.2 or later which contains the fix
• Apply security patches from your distribution vendor (Debian DSA-5448, DSA-5480, or LTS announcements)
• Restrict local access to systems running vulnerable kernel versions
• Monitor systems for signs of exploitation while patches are being deployed

Patch Information

The vulnerability has been addressed in the Linux kernel through commit 43ec16f1450f4936025a9bdf1a273affdb9732c1. This fix is included in Linux kernel version 6.3.2 and has been backported to various distribution kernels.

Patch resources:

• Linux Kernel Commit 43ec16f1450
• Kernel ChangeLog 6.3.2
• Debian Security Advisory DSA-5448
• Debian Security Advisory DSA-5480
• NetApp Security Advisory NTAP-20230824-0006

Workarounds

• Limit local user access to systems until patches can be applied
• Restrict access to relay filesystem interfaces where possible using file permissions or SELinux/AppArmor policies
• Consider disabling relayfs functionality if not required for system operations
• Implement network segmentation to limit lateral movement if a system is compromised

# Check current kernel version
uname -r

# Update kernel on Debian/Ubuntu systems
sudo apt update && sudo apt upgrade linux-image-$(uname -r)

# Reboot to apply new kernel
sudo reboot