Threats / Cisco / CVE-2020-3566
CVE-2020-3566
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-06-22
Cisco IOS XR vulnerability
Cisco IOS XR improperly handles IGMP packets in DVMRP, allowing unauthenticated remote attackers to crash the IGMP process or exhaust memory, causing denial of service.
Verdict
Today item — known-exploited.
An unauthenticated remote attacker can send crafted IGMP packets to trigger resource exhaustion or immediate process termination in Cisco IOS XR systems, disrupting multicast routing availability without authentication requirements.
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
2 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03).
Probability (EPSS)
EPSS 0.03959 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
Affected: Cisco, IOS XR. Confirm exact fixed builds in the vendor advisory.
Weakness (CWE)
Mapped to CWE-400 Uncontrolled Resource Consumption — weakness family: Resource / availability.CWE assignment from the public NVD record; the weakness class drives how the flaw is exploited.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I send malformed IGMP packets to the target IOS XR device over the network.
Business
Network multicast services become unavailable, disrupting video distribution, IPTV, or other group communication applications.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I exploit improper packet handling to exhaust memory or crash the IGMP process on the routing device.
Business
Router instability forces emergency maintenance windows and potential failover to backup infrastructure, increasing operational costs.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05