CVE-2023-2162: Linux Kernel Use-After-Free Vulnerability

CVE-2023-2162 Overview

CVE-2023-2162 is a use-after-free vulnerability discovered in the Linux Kernel's SCSI sub-component, specifically within the iscsi_sw_tcp_session_create function located in drivers/scsi/iscsi_tcp.c. This memory corruption flaw allows a local attacker to leak sensitive kernel internal information, potentially exposing critical system data that could be leveraged for further exploitation.

Critical Impact

Local attackers with low privileges can exploit this use-after-free condition to read sensitive kernel memory, potentially disclosing kernel addresses, cryptographic material, or other privileged information that could facilitate privilege escalation attacks.

Affected Products

• Linux Kernel versions prior to the security patch
• Linux Kernel 6.2 (including release candidates RC1 through RC5)
• Debian-based distributions using vulnerable kernel versions

Discovery Timeline

• April 19, 2023 - CVE-2023-2162 published to NVD
• March 19, 2025 - Last updated in NVD database

Technical Details for CVE-2023-2162

Vulnerability Analysis

This use-after-free vulnerability (CWE-416) occurs in the iSCSI software TCP session creation pathway within the Linux Kernel. The flaw exists because memory is accessed after it has been freed during the iSCSI session initialization process. When the iscsi_sw_tcp_session_create function handles session creation, improper memory management can result in references to freed memory objects.

The vulnerability requires local access to exploit, meaning an attacker must already have some level of access to the target system. While this limits the attack surface compared to remotely exploitable flaws, the ability to leak kernel memory makes this vulnerability significant for local privilege escalation chains.

Root Cause

The root cause lies in improper memory lifecycle management within the iSCSI TCP session creation code. When a session is created, certain memory structures may be freed prematurely while still being referenced by other parts of the code. This creates a dangling pointer situation where subsequent operations attempt to read from memory that has already been deallocated and potentially reallocated for other purposes.

The SCSI subsystem's handling of iSCSI software TCP sessions does not properly synchronize the freeing of session-related structures with their usage, leading to a temporal safety violation where freed memory is accessed.

Attack Vector

The attack vector is local, requiring an attacker to have local access to the vulnerable system. The exploitation involves triggering the vulnerable code path in iscsi_sw_tcp_session_create to cause the kernel to access freed memory. Since no user interaction is required and the attack complexity is low, an attacker with basic local privileges can reliably trigger the vulnerability.

The information disclosed through this vulnerability could include kernel memory layout information (useful for bypassing KASLR), kernel data structures, or other sensitive information stored in kernel memory. This leaked data could be combined with other vulnerabilities to achieve privilege escalation.

Detection Methods for CVE-2023-2162

Indicators of Compromise

• Unusual access patterns to iSCSI-related kernel functions from unprivileged processes
• Unexpected kernel memory access errors or warnings in system logs related to the SCSI subsystem
• Abnormal iSCSI session creation activity from non-administrative users
• Kernel oops or warnings referencing iscsi_sw_tcp_session_create or related functions

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/kern.log) for use-after-free warnings or SCSI subsystem errors
• Implement kernel address sanitizer (KASAN) on development and test systems to detect memory safety violations
• Deploy endpoint detection solutions capable of monitoring kernel-level behavior anomalies
• Review audit logs for unexpected iSCSI-related system calls from unauthorized processes

Monitoring Recommendations

• Enable comprehensive kernel logging for the SCSI subsystem to capture anomalous behavior
• Configure SentinelOne agents to monitor for suspicious local privilege escalation attempts
• Implement file integrity monitoring on critical kernel modules and iSCSI configuration files
• Set up alerts for failed or unusual iSCSI session creation attempts

How to Mitigate CVE-2023-2162

Immediate Actions Required

• Update the Linux Kernel to a patched version that addresses CVE-2023-2162
• Review and restrict local user access to minimize the attack surface for local exploitation
• Apply vendor-provided security patches from distribution maintainers (Debian, Red Hat, Ubuntu, etc.)
• Consider disabling iSCSI functionality if not required in your environment

Patch Information

Patches for this vulnerability have been released through the Linux kernel security team and downstream distributions. The Linux SCSI Mailing List Post contains details about the fix. Additionally, Debian has released advisories addressing this vulnerability for their supported distributions, as documented in the Debian LTS Advisory May 2023.

Organizations should check their distribution's security advisories and apply the appropriate kernel updates. For systems running custom-compiled kernels, ensure you are using a kernel version that includes the fix for this use-after-free condition.

Workarounds

• Disable the iscsi_tcp kernel module if iSCSI functionality is not required: modprobe -r iscsi_tcp
• Restrict local user access to systems where the vulnerability cannot be immediately patched
• Implement strict access controls and the principle of least privilege to limit potential attackers' capabilities
• Use kernel security modules (SELinux, AppArmor) to restrict access to iSCSI-related system calls

# Disable the vulnerable iSCSI TCP module if not needed
sudo modprobe -r iscsi_tcp

# Blacklist the module to prevent automatic loading
echo "blacklist iscsi_tcp" | sudo tee /etc/modprobe.d/blacklist-iscsi-tcp.conf

# Update initramfs to apply the blacklist
sudo update-initramfs -u