CVE-2023-2156 Overview
A flaw was found in the networking subsystem of the Linux kernel within the handling of the RPL (Routing Protocol for Low-Power and Lossy Networks) protocol. This issue results from the lack of proper handling of user-supplied data, which can lead to an assertion failure. This may allow an unauthenticated remote attacker to create a denial of service condition on the system.
Critical Impact
Unauthenticated remote attackers can cause system-wide denial of service by triggering an assertion failure in the Linux kernel's RPL protocol handling, potentially disrupting critical infrastructure services.
Affected Products
- Linux Kernel (multiple versions)
- Red Hat Enterprise Linux 9.0
- Fedora 38
- Debian Linux 10.0
Discovery Timeline
- May 9, 2023 - CVE-2023-2156 published to NVD
- November 21, 2024 - Last updated in NVD database
Technical Details for CVE-2023-2156
Vulnerability Analysis
The vulnerability exists in the Linux kernel's networking subsystem, specifically within the implementation of the RPL protocol. RPL is an IPv6 routing protocol designed for low-power and lossy networks (LLNs), commonly used in IoT environments. The flaw stems from improper handling of user-supplied data during protocol processing, which triggers an assertion failure (CWE-617: Reachable Assertion).
When specially crafted network packets are sent to a vulnerable system, the kernel's RPL handling code encounters an unexpected condition that causes an assertion to fail. Unlike typical input validation vulnerabilities that might allow code execution, this particular flaw causes the kernel to halt or panic, resulting in a complete denial of service condition.
Root Cause
The root cause of CVE-2023-2156 is a reachable assertion (CWE-617) within the RPL protocol implementation. Assertions are debugging checks that should never be triggered during normal operation. However, the vulnerable code path contains an assertion that can be reached by processing malformed or unexpected RPL protocol messages. The assertion failure occurs because the code assumes certain invariants about incoming data that an attacker can violate by crafting malicious packets. This indicates a gap between the expected input constraints and the actual validation performed before reaching the assertion.
Attack Vector
The attack can be performed remotely over the network without requiring authentication or user interaction. An attacker can exploit this vulnerability by sending specially crafted RPL protocol packets to a target system. Since RPL operates at the network layer and the vulnerability requires no prior privileges, any system with the RPL protocol enabled and reachable over the network is potentially vulnerable. The attack is particularly concerning for IoT deployments and network edge devices where RPL is commonly used.
The vulnerability manifests in the kernel's packet processing path for RPL protocol messages. When malformed data reaches the assertion check, the kernel triggers a failure condition that results in system unavailability. For detailed technical analysis, refer to the Zero Day Initiative Advisory ZDI-23-547 and the discussions on the Openwall OSS Security mailing list.
Detection Methods for CVE-2023-2156
Indicators of Compromise
- Unexpected kernel panics or system crashes related to networking subsystem
- System log entries showing assertion failures in RPL-related kernel code
- Abnormal RPL protocol traffic patterns from external sources
- Repeated service disruptions without apparent cause on systems with RPL enabled
Detection Strategies
- Monitor kernel logs for assertion failure messages related to rpl or IPv6 routing components
- Implement network intrusion detection rules to identify malformed RPL protocol packets
- Deploy SentinelOne Singularity agents to detect kernel-level anomalies and crash behaviors
- Use packet capture analysis to baseline normal RPL traffic and alert on deviations
Monitoring Recommendations
- Enable kernel audit logging to capture crash events and their triggering network activity
- Configure alerting for unexpected system reboots or kernel panic events
- Monitor network traffic at ingress points for RPL protocol anomalies
- Implement SentinelOne's endpoint protection to correlate system crashes with network events
How to Mitigate CVE-2023-2156
Immediate Actions Required
- Apply the latest kernel patches from your Linux distribution vendor immediately
- If patching is not immediately possible, consider disabling RPL protocol support if not required
- Implement network filtering to block RPL traffic from untrusted sources
- Review network architecture to minimize exposure of RPL-enabled systems to external networks
Patch Information
Security patches are available from multiple vendors. Refer to the following advisories for patch details:
- Red Hat Bugzilla #2196292 - Red Hat tracking and patch information
- Debian Security Advisory DSA-5448 - Debian stable release patches
- Debian Security Advisory DSA-5453 - Additional Debian security updates
- Debian LTS Announcement August 2023 - Long-term support release patches
- NetApp Security Advisory NTAP-20230622-0001 - NetApp product patches
Workarounds
- Disable RPL protocol support in the kernel if not required for your environment
- Implement network segmentation to isolate RPL-enabled devices from untrusted networks
- Deploy firewall rules to filter incoming IPv6 RPL packets at network boundaries
- Use network access control lists to restrict RPL traffic to known trusted sources only
# Check if RPL module is loaded
lsmod | grep rpl
# Disable RPL protocol support (if not needed)
echo "blacklist rpl" >> /etc/modprobe.d/blacklist-rpl.conf
modprobe -r rpl
# Block RPL traffic at the firewall level (IPv6)
ip6tables -A INPUT -p ipv6-route --rt-type 3 -j DROP
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
