Cisco IOS XR DVMRP Memory Exhaustion and IGMP Process Crash Vulnerability (CVE-2020-3569) Analysis & Mitigation Guide
Executive & SecOps Summary
SECOPS ASSESSMENTCisco IOS XR Software with the Distance Vector Multicast Routing Protocol (DVMRP) feature enabled
An unauthenticated, remote attacker can cause an immediate crash of the IGMP process or exhaust system memory, leading to instability in critical routing protocols and denial of service (DoS)
Apply official Cisco software updates, disable DVMRP multicast routing where not required, or implement IGMP packet filtering ACLs
Affected Products & Version Scope
Remediation & Live Workaround Commands
PATCH & WORKAROUND1. Official Patch & Version Upgrade Commands
Upgrade to the latest Cisco IOS XR software release that addresses this vulnerability. Use the following commands to verify the version and apply Software Maintenance Upgrades (SMUs).
# Verify current IOS XR version and active packages
show install active summary
# Add and activate the appropriate SMU patch (Example)
install add source tftp://10.1.1.10/asr9k-px-6.6.3.sp12.smu
install activate asr9k-px-6.6.3.sp12.smu
install commit2. Temporary Workaround & Hardening Configuration
If patching cannot be performed immediately, implement an inbound Access Control List (ACL) to filter out unauthorized IGMP/DVMRP traffic or disable DVMRP processing.
# Enter global configuration mode
configure terminal
# Apply DVMRP boundary filtering under multicast routing
router multicast-routing
address-family ipv4
interface GigabitEthernet0/0/0/0
boundary dvmrp-filter
!
commit
# Define and apply an ACL to block untrusted DVMRP traffic
ipv4 access-list ACL-BLOCK-DVMRP
deny igmp any any dvmrp
permit ip any any
commit3. Log Audit & IoC Verification Commands
Monitor system memory consumption and check for unexpected restarts of the IGMP process to detect potential exploitation attempts.
# Check memory usage and status of the IGMP process
show processes igmp
# Search system logs for IGMP crashes or memory exhaustion warnings
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Technical Root Cause & Exploitation Mechanics
1. Vulnerability Overview & Root Cause
This vulnerability (CVE-2020-3569) exists in the Distance Vector Multicast Routing Protocol (DVMRP) implementation of Cisco IOS XR Software. It is caused by improper handling and validation of incoming IGMP packets (CWE-400, CWE-770). The system fails to properly manage memory allocation when parsing crafted IGMP traffic, leading to memory leaks or immediate process termination.
2. Exploitation Mechanics & Attack Scenario
An unauthenticated remote attacker can exploit this vulnerability by transmitting specially crafted IGMP DVMRP packets to an affected device. When these packets are processed by the IGMP daemon, they trigger an unhandled exception or continuous memory allocation without deallocation. This vulnerability is actively exploited in the wild and is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.
3. Infrastructure & Business Impact
If the IGMP process crashes or memory exhaustion occurs, multicast routing functionality is severely degraded. Furthermore, the resulting Out-Of-Memory (OOM) condition can impact other critical system processes running on the device, including interior and exterior routing protocols (such as BGP or OSPF), leading to complete network outage and routing instability.
Official Vendor Advisories & References
Multiple vulnerabilities in the Distance Vector Multicast Routing Protocol (DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to either immediately crash the Internet Group Management Protocol (IGMP) process or make it consume available memory and eventually crash. The memory consumption may negatively impact other processes that are running on the device. These vulnerabilities are due to the incorrect handling of IGMP packets. An attacker could exploit these vulnerabilities by sending crafted IGMP traffic to an affected device. A successful exploit could allow the attacker to immediately crash the IGMP process or cause memory exhaustion, resulting in other processes becoming unstable. These processes may include, but are not limited to, interior and exterior routing protocols. Cisco will release software updates that address these vulnerabilities.
Frequently Asked SecOps Questions (CVE-2020-3569)
FAQQ1. How critical is CVE-2020-3569 and is it actively exploited in the wild?
CVE-2020-3569 is rated CVSS 8.6 (HIGH) with a 30-day EPSS exploitation probability of 3.3%. It is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, requiring immediate emergency remediation.
Q2. Which vendors and products are affected by CVE-2020-3569?
Primary impacted vendors include cisco across ios_xr. Scope summary: All Cisco IOS XR Software releases configured with the DVMRP feature and capable of receiving IGMP traffic
Q3. What temporary mitigations or workarounds exist for CVE-2020-3569 before patching?
[Mitigation] Apply official Cisco software updates, disable DVMRP multicast routing where not required, or implement IGMP packet filtering ACLs Follow the CLI remediation commands and interactive SecOps checklist on this page to restrict exposure prior to your maintenance window.
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