Cisco IOS and IOS XE IKEv2 Packet Processing Remote Denial of Service and Memory Leak Vulnerability (CVE-2018-0158)
Executive & SecOps Summary
SECOPS ASSESSMENTCisco devices running Cisco IOS or Cisco IOS XE Software with the IKEv2 protocol enabled.
An unauthenticated, remote attacker can trigger a continuous memory leak by sending crafted IKEv2 packets, eventually causing a device reload and a complete Denial of Service (DoS) condition.
Apply the official Cisco software updates or restrict access to IKEv2 ports (UDP 500/4500) using Infrastructure Access Control Lists (iACLs).
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Download the recommended fixed release from the Cisco Software Center. Use the following commands to download the secure IOS XE image via TFTP and update the boot path.
# Download the secure IOS XE image from a TFTP server
copy tftp: flash:
Address or name of remote host? 192.168.1.100
Source filename? cat3k_caa-universalk9.16.06.05.SPA.bin
Destination filename [cat3k_caa-universalk9.16.06.05.SPA.bin]?
# Configure the system to boot from the new image
configure terminal
no boot system
boot system flash:cat3k_caa-universalk9.16.06.05.SPA.bin
end
write memory
reload2. Temporary Workaround & Hardening Configuration
If patching cannot be performed immediately, implement an Infrastructure ACL (iACL) to restrict IKEv2 traffic (UDP ports 500 and 4500) only to trusted peer IP addresses.
# Define an ACL to permit only trusted VPN peers
ip access-list extended LIMIT_IKEV2
permit udp 203.0.113.0 0.0.0.255 any eq non500-isakmp
permit udp 203.0.113.0 0.0.0.255 any eq isakmp
deny udp any any eq non500-isakmp
deny udp any any eq isakmp
permit ip any any
exit
# Apply the ACL to the external interface
interface GigabitEthernet0/0
ip access-group LIMIT_IKEV2 in
end3. Log Audit & IoC Verification Commands
Monitor the device's memory utilization regularly to detect potential memory leaks associated with IKEv2 processes.
# Check overall system memory statistics
show memory statistics
# Inspect memory allocation specifically for IKEv2 processes
show processes memory | include IKEv2Stop Exposing VPN Ports to the Internet — Switch to Zero-Trust Access
Eliminate public-facing VPN concentrators and firewall management ports with identity-first Zero-Trust Network Access.
Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability exists in the Internet Key Exchange Version 2 (IKEv2) module of Cisco IOS and Cisco IOS XE Software. It is caused by improper input validation (CWE-20) and improper resource release (CWE-401) during the parsing of specific IKEv2 negotiation packets. The system fails to free allocated memory buffers when processing these malformed packets, leading to a progressive memory leak.
2. Exploitation Mechanics & Attack Scenario
An unauthenticated remote attacker can exploit this vulnerability by sending crafted IKEv2 packets to the target device's active IKEv2 ports (UDP 500 and UDP 4500 for NAT-T). Because the vulnerability does not require authentication, the attacker can continuously stream these packets. Each processed packet leaks a portion of system memory, eventually exhausting the control plane memory and forcing the device to crash and reload to recover.
3. Infrastructure & Business Impact
As this vulnerability is listed in the CISA KEV (Known Exploited Vulnerabilities) catalog, it has been actively exploited in the wild. A successful exploit directly impacts business continuity by disabling critical Site-to-Site and Client-to-Site VPN tunnels, isolating remote branches, and disrupting secure enterprise communications.
Official Vendor Advisories & References
A vulnerability in the Internet Key Exchange Version 2 (IKEv2) module of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a memory leak or a reload of an affected device that leads to a denial of service (DoS) condition. The vulnerability is due to incorrect processing of certain IKEv2 packets. An attacker could exploit this vulnerability by sending crafted IKEv2 packets to an affected device to be processed. A successful exploit could cause an affected device to continuously consume memory and eventually reload, resulting in a DoS condition. Cisco Bug IDs: CSCvf22394.
Frequently Asked SecOps Questions (CVE-2018-0158)
FAQQ1. How critical is CVE-2018-0158 and is it actively exploited in the wild?
CVE-2018-0158 is rated CVSS 8.6 (HIGH) with a 30-day EPSS exploitation probability of 7.2%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2018-0158?
Primary impacted vendors include cisco across ios, ios xe. Scope summary: All Cisco IOS and Cisco IOS XE Software releases with an active IKEv2 configuration (Cisco Bug ID: CSCvf22394).
Q3. What temporary mitigations or workarounds exist for CVE-2018-0158 before patching?
[Mitigation] Apply the official Cisco software updates or restrict access to IKEv2 ports (UDP 500/4500) using Infrastructure Access Control Lists (iACLs). Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
Generate an Internal Engineering Notice or CISO Report for CVE-2018-0158
Instantly format this advisory into an executive CISO summary or engineering patch ticket.
🔗 Related Advisories in Similar Stack (cisco)
View Category →Cisco Identity Services Engine (ISE) Critical Authentication Bypass Vulnerability (CVE-2026-76460)
[Affected Scope] Cisco Identity Services Engine (ISE) web-based management interface and API endpoints.
Cisco Catalyst SD-WAN Peering Authentication Bypass Vulnerability (CVE-2026-20182)
[Affected Scope] Cisco Catalyst SD-WAN Controller (formerly vSmart), Manager (formerly vManage), and Validator (formerly vBond)
Cisco Secure Firewall Management Center (FMC) Insecure Deserialization Vulnerability (CVE-2026-20131, CVSS 10.0) - Remote Code Execution and Root Privilege Escalation
[Affected Scope] Web-based management interface of Cisco Secure Firewall Management Center (FMC) Software.
Cisco Secure Firewall Management Center (FMC) Authentication Bypass and Root RCE Vulnerability (CVE-2026-20079)
[Affected Scope] Web-based management interface of Cisco Secure Firewall Management Center (FMC) Software
Subscribe to Daily Vulnerability Briefings & KEV Alerts
Concise morning briefings for SecOps, DevSecOps, and SRE teams covering newly exploited CVEs and mitigation priorities.