CVE-2020-3566

Read full 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.

CVSS 8.6 (HIGH) KEV: KNOWN CATALOG

Attention and evidence

HYPE SCORE

0.0/10

REALITY · THREAT PRIORITY

8.3/10

General review priority; not probability

Evidence confidence: Exploitation recorded

Why this priority?

Recorded exploitation baseline: +7.00
Technical severity: CVSS 8.6: +1.29
Fresh EPSS: 3.70%: +0.02

General review priority, not probability, victim count or asset-specific risk. A range covers missing CVSS/EPSS inputs within the current evidence state.

Sources: 3 documents and public datasets.

Hype components

Headline sample (25%)

0/100

Press, 30 days (60%)

0/100

Grounded branding (15%)

0/100

HYPE TOTAL0/100

Sources and documents

BleepingComputer

Press · 04 Aug 2021, 07:00 · Cisco fixes critical, high severity pre-auth flaws in VPN routers - BleepingComputer

BleepingComputer

Press · 29 Sep 2020, 07:00 · Cisco fixes actively exploited bugs in carrier-grade routers - BleepingComputer

Ars Technica

Press · 31 Aug 2020, 07:00 · Attackers are trying to exploit a high-severity zeroday in Cisco gear - Ars Technica

Score evolution

● Hype ● Reality

Earlier evidence-support scores are retained in history; this chart shows only the current priority definition.

First record: hype 0.0 · reality 8.3 (2026-11-02 15:12). The curve appears once the score changes.

Public exploit evidence

Public exploit entries / repo candidates

See 2 repos with metrics

Repository	Stars	Forks	Language	Updated
Diekgbbtt/CVE-2020-35667-PoC	0	0	Python	16 Oct 2025, 22:32
stefan-500/teamcity-idea-cve-2020-35667-poc	0	0	Python	07 Nov 2025, 10:19

Evidence context and dated references

Reality is general threat/review priority, combining observed exploitation, CVSS severity and fresh EPSS. Evidence confidence is separate. This is not calibrated risk, a victim count or an asset-specific assessment. A range reflects missing numeric inputs.

Evidence in context

Confidence in exploitation evidence: Exploitation recorded
Priority basis: Recorded exploitation; CVSS 8.6; EPSS 3.7%
Attention, last 30 days: 0 distinct story titles; 0 press documents; 0 publisher domains.
Technical potential: network access, no prior privileges, no user interaction.
Observed activity: Exploitation recorded in CISA KEV.
Known scale: Not quantified.
Evidence confidence basis: Trusted exploitation confirmation

Score evaluated: 2026-11-05 13:58:18.514971+00:00 · EPSS snapshot: 2026-11-05T12:03:04Z

Source event timeline

Published

29 Aug 2020, 15:15

First press mention

31 Aug 2020, 07:00

Latest press mention

04 Aug 2021, 07:00

Added to the CISA KEV catalog

03 Nov 2021, 00:00

Score calculated

05 Nov 2026, 13:58

PoCs on GitHub

2 repositories