CVE-2023-6610: Linux Kernel Information Disclosure Flaw

CVE-2023-6610 Overview

An out-of-bounds read vulnerability was discovered in the Linux Kernel's SMB client implementation, specifically within the smb2_dump_detail function located in fs/smb/client/smb2ops.c. This flaw allows a local attacker with low privileges to read memory beyond allocated buffer boundaries, potentially causing system crashes or exposing sensitive kernel memory contents. The vulnerability affects systems utilizing SMB/CIFS file sharing functionality and represents a significant security concern for enterprise Linux deployments.

Critical Impact

Local attackers can exploit this out-of-bounds read to crash the system (denial of service) or leak sensitive kernel information that could facilitate further attacks.

Affected Products

• Linux Kernel (all affected versions)
• Red Hat Enterprise Linux 8.0
• Red Hat Enterprise Linux 9.0

Discovery Timeline

• December 8, 2023 - CVE-2023-6610 published to NVD
• November 21, 2024 - Last updated in NVD database

Technical Details for CVE-2023-6610

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory safety issue that occurs when the smb2_dump_detail function accesses memory locations outside the intended buffer boundaries. The flaw resides in the SMB2 client operations code, which handles the parsing and processing of SMB protocol responses.

The vulnerability requires local access to exploit, meaning an attacker must have the ability to execute code on the target system. Once triggered, the out-of-bounds read can expose adjacent kernel memory contents, potentially revealing sensitive information such as kernel addresses, cryptographic material, or data from other processes. Additionally, reading invalid memory regions can cause kernel panics, resulting in system crashes and service disruption.

The impact is twofold: confidentiality is compromised through potential information disclosure, and availability is threatened through denial of service conditions. While no integrity impact is associated with this read-only vulnerability, the leaked information could enable more sophisticated follow-up attacks.

Root Cause

The root cause stems from insufficient bounds checking in the smb2_dump_detail function when processing SMB2 protocol data. The function fails to properly validate buffer lengths before accessing memory, allowing reads past the allocated buffer boundaries. This is a classic example of improper input validation in kernel-space code where malformed or crafted SMB responses can trigger the vulnerable code path.

Attack Vector

Exploitation requires local access with low privileges. An attacker could trigger the vulnerability by:

1. Mounting a malicious SMB share or interacting with a compromised SMB server
2. Sending specially crafted SMB2 responses that cause the kernel client to mishandle buffer lengths
3. The smb2_dump_detail function processes the malformed response without proper bounds checking
4. The out-of-bounds read either leaks kernel memory or causes a crash

The vulnerability is particularly concerning in multi-tenant environments where local users might attempt to escalate privileges or extract sensitive information from kernel memory.

Detection Methods for CVE-2023-6610

Indicators of Compromise

• Unexpected kernel panics or crashes related to SMB/CIFS subsystem operations
• Abnormal memory access patterns in kernel logs associated with smb2ops.c
• System instability when interacting with SMB file shares
• Kernel oops messages referencing the SMB client code path

Detection Strategies

• Monitor kernel logs (dmesg, /var/log/messages) for out-of-bounds access warnings or SMB-related crashes
• Implement kernel auditing to track SMB mount operations and client activities
• Deploy endpoint detection solutions capable of identifying kernel memory access anomalies
• Use SentinelOne's Singularity platform to detect and respond to exploitation attempts targeting kernel vulnerabilities

Monitoring Recommendations

• Enable verbose logging for CIFS/SMB client operations to identify suspicious activity
• Configure alerting for unexpected kernel crashes or restarts
• Monitor network traffic for connections to untrusted SMB servers
• Implement file integrity monitoring on critical system files and kernel modules

How to Mitigate CVE-2023-6610

Immediate Actions Required

• Apply the latest kernel security patches from your distribution vendor immediately
• Limit SMB mount operations to trusted servers only through network policies
• Restrict local user access to systems where SMB functionality is critical
• Consider disabling unnecessary SMB client functionality if not required for operations

Patch Information

Multiple security advisories have been released to address this vulnerability:

• Red Hat Security Advisory RHSA-2024:0723
• Red Hat Security Advisory RHSA-2024:0724
• Red Hat Security Advisory RHSA-2024:0725
• Red Hat Security Advisory RHSA-2024:0881
• Red Hat Security Advisory RHSA-2024:0897
• Red Hat Security Advisory RHSA-2024:1248
• Red Hat Security Advisory RHSA-2024:1404
• Red Hat Security Advisory RHSA-2024:2094

For additional technical details, refer to Kernel Bugzilla Report #218219 and Red Hat Bugzilla Report #2253614.

Workarounds

• Restrict access to SMB mounts through firewall rules and network segmentation
• Disable the CIFS/SMB kernel module if file sharing functionality is not required: modprobe -r cifs
• Implement strict access controls limiting which users can mount SMB shares
• Use network isolation to prevent connections to untrusted SMB servers

# Disable CIFS kernel module if not needed
sudo modprobe -r cifs

# Prevent automatic loading of CIFS module
echo "install cifs /bin/false" | sudo tee /etc/modprobe.d/disable-cifs.conf

# Apply kernel updates on Red Hat-based systems
sudo yum update kernel

# Apply kernel updates on Debian-based systems
sudo apt update && sudo apt upgrade linux-image-*