CVE-2023-39197: Linux Kernel Information Disclosure Flaw

CVE-2023-39197 Overview

An out-of-bounds read vulnerability was discovered in the Netfilter Connection Tracking (conntrack) subsystem of the Linux kernel. This security flaw enables a remote attacker to read beyond allocated memory boundaries, potentially disclosing sensitive kernel memory information via specially crafted DCCP (Datagram Congestion Control Protocol) network traffic.

Critical Impact

Remote attackers can exploit this vulnerability to access sensitive information from kernel memory without authentication, potentially exposing cryptographic keys, session data, or other confidential information processed by the system.

Affected Products

• Linux Kernel (multiple versions)
• Fedora 38
• Systems running Netfilter with DCCP protocol support enabled

Discovery Timeline

• 2024-01-23 - CVE-2023-39197 published to NVD
• 2024-11-21 - Last updated in NVD database

Technical Details for CVE-2023-39197

Vulnerability Analysis

This vulnerability is classified as CWE-125 (Out-of-Bounds Read), a memory safety issue that occurs when the software reads data past the end or before the beginning of an intended buffer. In the context of the Linux kernel's Netfilter conntrack module, this flaw manifests during the processing of DCCP protocol packets.

The Netfilter connection tracking system is responsible for maintaining state information about network connections passing through the Linux firewall. When handling DCCP protocol traffic, the vulnerable code path fails to properly validate data boundaries before performing read operations, allowing an attacker to trigger reads beyond the allocated buffer.

The vulnerability can be exploited remotely over the network without requiring any authentication or user interaction, making it particularly concerning for systems exposed to untrusted network traffic.

Root Cause

The root cause of this vulnerability lies in improper bounds checking within the DCCP connection tracking code in the Netfilter subsystem. When processing certain DCCP packet types, the kernel fails to verify that the data being accessed falls within the expected memory boundaries. This allows crafted network packets to trigger out-of-bounds memory reads, potentially leaking sensitive kernel memory contents back to the attacker.

Attack Vector

The attack vector for CVE-2023-39197 is network-based, requiring no privileges or user interaction. An attacker can exploit this vulnerability by sending specially crafted DCCP protocol packets to a target system running a vulnerable Linux kernel with Netfilter connection tracking enabled.

The attack flow involves:

1. Identifying a target system with DCCP protocol handling enabled in the kernel
2. Crafting malicious DCCP packets designed to trigger the out-of-bounds read condition
3. Sending these packets to the target system over the network
4. Analyzing responses or side channels to extract leaked kernel memory information

Since no verified code examples are available for this vulnerability, readers should consult the Red Hat CVE-2023-39197 Advisory and Red Hat Bug Report #2218342 for detailed technical information about the exploitation mechanism.

Detection Methods for CVE-2023-39197

Indicators of Compromise

• Unusual DCCP protocol traffic patterns, especially from external sources
• Kernel log messages indicating memory access violations or warnings in the Netfilter/conntrack subsystem
• Unexpected network connections or traffic spikes involving DCCP protocol (IP protocol number 33)
• System instability or crashes potentially related to memory access issues in network packet processing

Detection Strategies

• Monitor network traffic for anomalous DCCP protocol activity, particularly from untrusted sources
• Deploy intrusion detection rules to identify malformed or suspicious DCCP packets targeting conntrack functionality
• Implement kernel auditing to detect potential exploitation attempts against the Netfilter subsystem
• Use SentinelOne's behavioral AI engine to detect exploitation patterns and anomalous kernel memory access

Monitoring Recommendations

• Enable comprehensive logging for Netfilter and connection tracking events
• Configure network monitoring tools to alert on DCCP protocol traffic if not normally expected in your environment
• Implement kernel-level monitoring using tools like auditd or eBPF-based solutions to track suspicious system calls
• Utilize SentinelOne Singularity Platform for real-time endpoint detection and response capabilities

How to Mitigate CVE-2023-39197

Immediate Actions Required

• Update the Linux kernel to the latest patched version from your distribution vendor
• If DCCP protocol support is not required, disable it by blacklisting the dccp kernel module: echo "install dccp /bin/true" >> /etc/modprobe.d/disable-dccp.conf
• Apply firewall rules to block incoming DCCP traffic from untrusted networks
• Monitor systems for signs of exploitation while patches are being deployed

Patch Information

Patches for CVE-2023-39197 have been made available through the Linux kernel maintainers and major distribution vendors. Organizations should consult the Red Hat CVE-2023-39197 Advisory for specific patch information and affected version details. Additional technical context is available in Red Hat Bug Report #2218342.

Workarounds

• Disable the DCCP kernel module if not required by your applications
• Implement network-level filtering to block DCCP protocol traffic at the perimeter
• Use network segmentation to limit exposure of vulnerable systems to untrusted traffic
• Consider using kernel live patching solutions like kpatch or livepatch if available for your distribution

# Disable DCCP kernel module (workaround)
# Add to /etc/modprobe.d/disable-dccp.conf
echo "install dccp /bin/true" | sudo tee /etc/modprobe.d/disable-dccp.conf
echo "install dccp_ipv4 /bin/true" | sudo tee -a /etc/modprobe.d/disable-dccp.conf
echo "install dccp_ipv6 /bin/true" | sudo tee -a /etc/modprobe.d/disable-dccp.conf

# Verify module is not loaded
lsmod | grep dccp

# If loaded, remove the module
sudo modprobe -r dccp_ipv6 dccp_ipv4 dccp