CVE-2024-20311 Overview
A vulnerability in the Locator ID Separation Protocol (LISP) feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause an affected device to reload. This vulnerability is due to the incorrect handling of LISP packets, enabling attackers to exploit the flaw by sending crafted LISP packets to vulnerable devices. A successful exploit results in a denial of service (DoS) condition as the device reloads unexpectedly.
The vulnerability can be exploited over either IPv4 or IPv6 transport, expanding the potential attack surface for organizations running affected Cisco networking equipment.
Critical Impact
Unauthenticated remote attackers can cause network infrastructure devices to reload, resulting in service disruption and potential network outages across enterprise environments.
Affected Products
- Cisco IOS Software (versions 15.1 through 15.9)
- Cisco IOS XE Software (versions 3.7 through 17.11)
- Cisco routers and switches running LISP-enabled configurations
Discovery Timeline
- March 27, 2024 - CVE-2024-20311 published to NVD
- July 30, 2025 - Last updated in NVD database
Technical Details for CVE-2024-20311
Vulnerability Analysis
This denial of service vulnerability exists within the LISP packet processing functionality of Cisco IOS and IOS XE operating systems. The Locator ID Separation Protocol (LISP) is a network architecture and protocol designed to improve scalability in large enterprise and service provider networks by separating device identity from device location.
The vulnerability stems from improper handling of malformed or specially crafted LISP packets. When the affected device receives these packets, the inadequate input validation causes the system to enter an error state, triggering an automatic device reload. This uncontrolled resource consumption pattern (CWE-674: Uncontrolled Recursion) allows remote attackers to repeatedly crash network devices without authentication.
The attack is particularly concerning because it requires no authentication and can be launched remotely across the network. The vulnerability affects both IPv4 and IPv6 transport, meaning dual-stack environments are vulnerable regardless of which protocol family is in use.
Root Cause
The root cause is classified under CWE-674 (Uncontrolled Recursion), indicating that the LISP packet processing code contains improper recursion handling or uncontrolled resource consumption when parsing maliciously crafted packet structures. This results in stack exhaustion or memory corruption that forces the device to reload.
Attack Vector
The attack vector is network-based with no authentication requirements. An attacker can exploit this vulnerability by:
- Identifying Cisco devices running LISP-enabled IOS or IOS XE software
- Crafting malicious LISP packets with specific malformed attributes
- Sending the crafted packets to the target device over IPv4 or IPv6
- The device processes the malformed packets, triggering the vulnerability
- The affected device reloads, causing service interruption
The attack requires network access to reach the LISP service on the target device but does not require valid credentials or prior authentication, making it accessible to any attacker with network connectivity.
Detection Methods for CVE-2024-20311
Indicators of Compromise
- Unexpected device reloads with crash dump files referencing LISP packet processing functions
- Syslog entries showing process crashes related to LISP components
- Network monitoring alerts for unusual LISP traffic patterns or volumes
- Multiple consecutive device restarts without administrative action
Detection Strategies
- Deploy network intrusion detection systems (IDS) with signatures for malformed LISP packet detection
- Monitor device syslog for LISP-related crash messages or unexpected reload events
- Implement NetFlow or sFlow analysis to identify anomalous LISP traffic patterns
- Configure SNMP traps for device reload events to enable rapid incident response
Monitoring Recommendations
- Enable detailed LISP protocol logging on affected devices to capture packet processing errors
- Configure centralized syslog collection to correlate reload events across multiple devices
- Establish baseline LISP traffic patterns to identify deviations that may indicate exploitation attempts
- Implement automated alerting for any unplanned device reloads in the network infrastructure
How to Mitigate CVE-2024-20311
Immediate Actions Required
- Review Cisco security advisory and determine if your devices are running vulnerable software versions
- Apply the appropriate software updates from Cisco as soon as possible
- Implement access control lists (ACLs) to restrict LISP traffic to trusted sources only
- Consider disabling LISP functionality on devices where it is not operationally required
Patch Information
Cisco has released security updates to address this vulnerability. Organizations should consult the Cisco Security Advisory for specific fixed software versions applicable to their deployment. The advisory provides detailed guidance on determining the appropriate upgrade path based on current software version and platform.
Affected versions span a wide range of Cisco IOS releases from 15.1(1)SY through 15.9(3)M7a and Cisco IOS XE releases from 3.7.0S through 17.11.99SW. Organizations should verify their current software version and plan upgrades according to Cisco's recommended fixed releases.
Workarounds
- Implement infrastructure ACLs to limit LISP protocol access to only authorized endpoints
- Deploy control plane policing (CoPP) to rate-limit LISP traffic and reduce the impact of potential attacks
- Isolate LISP-enabled devices on dedicated management networks where feasible
- Monitor for exploitation attempts while planning and executing software upgrades
# Example ACL to restrict LISP traffic (UDP port 4341/4342)
# Apply to appropriate interfaces based on network topology
access-list 101 permit udp host <trusted-source-ip> any eq 4341
access-list 101 permit udp host <trusted-source-ip> any eq 4342
access-list 101 deny udp any any eq 4341 log
access-list 101 deny udp any any eq 4342 log
access-list 101 permit ip any any
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
