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A vulnerability in the Distance Vector Multicast Routing Protocol (DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to exhaust process memory of an affected device. The vulnerability is due to insufficient queue management for Internet Group Management Protocol (IGMP) packets. An attacker could exploit this vulnerability by sending crafted IGMP traffic to an affected device. A successful exploit could allow the attacker to cause memory exhaustion, resulting in instability of other processes. These processes may include, but are not limited to, interior and exterior routing protocols. Cisco will release software updates that address this vulnerability.
Use CWE-400, Cisco vendor hub and Ios Xr product page to widen CVE-2020-3566 into its surrounding weakness, vendor, and product context.
Compare it with CVE-2025-20363, CVE-2025-20138 and CVE-2025-20154 for nearby disclosures in the same product family. Additional editorial context is available in The Weekly Cybersecurity Brief: January 30th, 2026.