High 8.6Known exploited (CISA KEV)Published Aug 29, 2020

CVE-2020-3566Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Updated under an hour ago (2026-10-19 11:10 UTC)

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It affects Cisco IOS XR Software and 1 other product. Add what you run to find out whether that includes you.

CISA lists it as known exploited since Nov 3, 2021; federal agencies had to remediate by May 3, 2022. Treat that date as your deadline.

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Exploited in the last 30 days

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.

CVSS: 8.6 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Weakness (CWE): CWE-400
Known exploited: Added to CISA KEV Nov 3, 2021; federal remediation due May 3, 2022Apply updates per vendor instructions.
EPSS (exploitation in the next 30 days): 3.70% (percentile 90)
Assigned by: cisco
NVD analysis: Analyzed
Record last updated: Oct 21, 2025
First seen by InfoSec Signals: Oct 9, 2026

Affected products

Affected products

Cisco Cisco IOS XR Software cisco:ios_xr_software (from the name)	all versions	CNA record
cisco ios_xr cisco:ios_xr	6.4.2	NVD

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dvmrp-memexh-dSmpdvfzvendor-advisory, x-refsource-cisco
https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3566us-government-resource

The CVE record on cve.org NVD's entry

The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.