Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability (CVE-2020-3566) | HOL Guard CVE

High severityKnown ExploitedCVE-2020-3566

Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Answer in brief

CVE-2020-3566 records a High severity vulnerability in Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability. The current sources mark it as known exploited. The current feed maps Cisco/Cisco IOS XR Software (generic). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Aug 29, 2020Updated Oct 21, 2025Source checked Sep 17, 2026First seen by HOL May 24, 2026Material review Oct 21, 2025

Upstream Advisory

Key facts

Risk: High
Exploitation: Known exploited
Affected software: 1 mapped package or product
Fix availability: Not reported

Why this deserves its current priority

A CVSS score is not reported in the current record. Known-exploitation status makes exposure review time-sensitive. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Cisco/Cisco IOS XR Software (generic). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
Cisco/Cisco IOS XR Softwaregeneric	n/a	Not reported

Recommended response

Check inventory. Check lockfiles and deployed manifests for Cisco/Cisco IOS XR Software.
Review the reported fix. Monitor this advisory for an available fix and review any installs of the affected package.

Evidence timeline and material changes

Published upstream
Aug 29, 2020
Evidence: source:cvelist:source_dates:source-dates:record
Source modified
Oct 21, 2025
Evidence: source:cvelist:source_dates:source-dates:record
First seen by HOL
May 24, 2026
Added to CISA KEV
Nov 3, 2021
Evidence: source:kev:kev:kev:record

Sources and claim methodology

Upstream source description

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.

Quoted source text, attributed separately from HOL analysis.