CVE-2020-3566

CRITICALNVD 8.69.0
EchelonGraph scoreHIGH confidence

“▲” beside the score: it is higher than NVD's CVSS score.

Score elevated to 9.0 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 8.6 retained for reference. The 9.0 is the floor for confirmed exploitation, not an impact rating: this CVE's impact severity (EG Severity) is CVSS 8.6 HIGH under NVD CVSS v3. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: CISA Known Exploited Vulnerabilities catalog, EPSS, GitHub Security Advisory, NVD CVSS v3
Trending — 3 sources updated this weekExploited in the wild

Also known asEUVD-2020-24837 (ENISA EUVD) · GHSA-mr9v-hqxh-vq2j (GitHub Security Advisories)Source: ENISA EUVD

9.0EG
EchelonGraph verdictMitigate nowTreat as an emergency — this is being exploited.
  • Actively exploited in the wild (CISA-KEV) — the reason this is sooner than the SSVC decision on this page at low or medium mission impact
CISA-KEV: ExploitedEPSS PROB: 3.7%CVSS: 8.6Exploit: No code on recordExposed services: Not assessed

No fix has been recorded since the CVE record was published in 2020 — use a compensating control (WAF / firewall / segmentation) and check the vendor's advisory.

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 v3
8.6
EG Score
9.0CRITICALhigh confidence
EG Risk
94
EG Risk 94/100

EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.

How it’s computed (value × EchelonGraph’s weight)
Severity86% × 45%
Impact severity (EG Severity): CVSS 8.6 of 10. Never the KEV-floored or EPSS-lifted EG Score.
Exploitation100% × 40%
Fixed at 100% for a CISA KEV listing: EchelonGraph's rule.
Automatability100% × 15%
CISA's SSVC Automatable value: yes (Vulnrichment).
SSVC (CISA's decision table, applied by EchelonGraph): Attend at low or medium mission impact; Act at high (mission-essential systems).
Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.
Action: No fix has been recorded since the CVE record was published in 2020. Check the vendor's advisory for a fixed release; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation sooner than your normal schedule at low or medium mission impact and as soon as possible at high.
EPSS PROB
3.7%
EPSS %ILE
89th
KEV
⚠ Exploited

What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)

The EG score (9.0): severity, escalated by confirmed exploitation. This CVE's 9.0 is the CISA KEV floor for confirmed exploitation, not an impact rating: its impact severity (EG Severity) is CVSS 8.6 HIGH.

EG Severity
8.6 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.NVD CVSS v3 · CVSS v3.0 or v3.1
EG Likelihood
3.7% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-11-01). FIRST's exploitation probability, not an EchelonGraph model.
Confirmed exploitation
CISA KEV and EG-KEV Tier 1 (exploited in the wild)Reported apart from the likelihood: an observed fact, not a probability.
EG Priority
SSVC Attend at medium mission impactAttend at low or medium mission impact; Act at high (mission-essential systems).CISA BOD 26-04: 3 days if the affected system is publicly exposed; 14 days if it is not.No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: this CVE is in CISA's KEV catalog, and CISA's required action for it, quoted below, applies whether or not a fix is released.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.

SSVC (CISA's decision table, applied by EchelonGraph)Attend at low or medium mission impact; Act at high (mission-essential systems).

No fix has been recorded since the CVE record was published in 2020. Check the vendor's advisory for a fixed release; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation sooner than your normal schedule at low or medium mission impact and as soon as possible at high.

Exploitation active (CISA Vulnrichment) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table

BOD 26-04 (CISA's remediation timeline, Table 1)3 days if the affected system is publicly exposed; 14 days if it is not.

No released fix is confirmed on this page, but CISA's timeline does not wait for a fix's release: this CVE is in CISA's KEV catalog, and CISA's required action for it, quoted below, applies whether or not a fix is released.

The score's inputs: In CISA KEV yes (CISA's KEV catalog) · Automatable yes (CISA Vulnrichment) · Technical impact partial (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it

CISA required action“Apply updates per vendor instructions.”

Quoted verbatim from CISA's Known Exploited Vulnerabilities catalog. CISA directs it at US federal civilian executive branch agencies under Binding Operational Directive (BOD) 26-04, which replaced BOD 22-01 on 10 June 2026; it is not EchelonGraph's advice. CISA's notes: https://nvd.nist.gov/vuln/detail/CVE-2020-3566

Published

August 29, 2020

Last Modified

October 28, 2025

Advisory Details (2)

Auto-updated Oct 26, 2026
⚠️ Actively exploited (CISA KEV, CISA Vulnrichment). No fix on record since 2020. Sources: cisa.
CISA🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3566

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 21× in last 7d / 133× in last 30d)

Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.

Showing the most recent 100 of 1,154 refreshes on record for this CVE.

A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 1,054 oldest rows on record are not shown and were not checked, so the counts can still include repeats.

  1. 2026-11-02 07:55 UTCEG score recompute
  2. 2026-11-02 07:55 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  3. 2026-11-01 16:29 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  4. 2026-11-01 06:42 UTCEG score recompute
  5. 2026-11-01 06:42 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  6. 2026-10-31 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  7. 2026-10-31 05:28 UTCEG score recompute
  8. 2026-10-31 05:28 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  9. 2026-10-30 16:29 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  10. 2026-10-30 04:15 UTCEG score recompute
  11. 2026-10-30 04:15 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  12. 2026-10-29 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  13. 2026-10-29 03:01 UTCEG score recompute
  14. 2026-10-29 03:01 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  15. 2026-10-28 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  16. 2026-10-28 01:48 UTCEG score recompute
  17. 2026-10-28 01:48 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  18. 2026-10-27 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  19. 2026-10-27 00:33 UTCEG score recompute
  20. 2026-10-27 00:32 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  21. 2026-10-26 16:27 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  22. 2026-10-25 23:19 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  23. 2026-10-25 18:43 UTCEG score recompute
  24. 2026-10-25 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  25. 2026-10-24 22:05 UTCEG score recompute
Show 75 more
  1. 2026-10-24 22:05 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  2. 2026-10-24 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  3. 2026-10-23 20:49 UTCEG score recompute
  4. 2026-10-23 20:49 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  5. 2026-10-23 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  6. 2026-10-22 19:35 UTCEG score recompute
  7. 2026-10-22 19:35 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  8. 2026-10-22 16:29 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  9. 2026-10-21 18:22 UTCEG score recompute
  10. 2026-10-21 18:22 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  11. 2026-10-21 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  12. 2026-10-20 17:09 UTCEG score recompute
  13. 2026-10-20 17:09 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  14. 2026-10-20 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  15. 2026-10-19 16:27 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  16. 2026-10-19 15:55 UTCEG score recompute
  17. 2026-10-19 15:55 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  18. 2026-10-18 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  19. 2026-10-18 14:40 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  20. 2026-10-18 09:23 UTCEG score recompute
  21. 2026-10-17 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  22. 2026-10-17 13:26 UTCEG score recompute
  23. 2026-10-17 13:26 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  24. 2026-10-16 16:33 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  25. 2026-10-16 12:11 UTCEG score recompute
  26. 2026-10-16 12:11 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  27. 2026-10-15 16:27 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  28. 2026-10-15 10:56 UTCEG score recompute
  29. 2026-10-15 10:56 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  30. 2026-10-14 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  31. 2026-10-14 09:42 UTCEG score recompute
  32. 2026-10-14 09:42 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  33. 2026-10-13 16:28 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  34. 2026-10-13 08:27 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  35. 2026-10-12 19:36 UTCEG score recompute
  36. 2026-10-12 16:29 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  37. 2026-10-12 07:14 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  38. 2026-10-12 03:14 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  39. 2026-10-11 23:14 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  40. 2026-10-11 19:16 UTCEG score recompute
  41. 2026-10-11 19:16 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  42. 2026-10-11 15:18 UTCEG score recompute
  43. 2026-10-11 15:18 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  44. 2026-10-11 13:43 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  45. 2026-10-11 11:20 UTCEG score recompute
  46. 2026-10-11 11:20 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  47. 2026-10-11 07:20 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  48. 2026-10-11 03:22 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  49. 2026-10-10 23:23 UTCEG score recompute
  50. 2026-10-10 23:23 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  51. 2026-10-10 19:56 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  52. 2026-10-10 19:24 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  53. 2026-10-10 15:26 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  54. 2026-10-10 11:27 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  55. 2026-10-10 07:30 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  56. 2026-10-10 03:28 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  57. 2026-10-09 23:31 UTCEG score recompute
  58. 2026-10-09 23:31 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  59. 2026-10-09 20:04 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  60. 2026-10-09 19:32 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  61. 2026-10-09 15:34 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  62. 2026-10-09 11:36 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  63. 2026-10-09 07:37 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  64. 2026-10-09 03:39 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  65. 2026-10-08 23:41 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  66. 2026-10-08 19:43 UTCEG score recompute
  67. 2026-10-08 19:43 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  68. 2026-10-08 16:38 UTCEPSS rescoreEPSS 3.7% · 89th percentile
  69. 2026-10-08 15:45 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  70. 2026-10-08 11:47 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  71. 2026-10-08 07:48 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  72. 2026-10-08 03:49 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  73. 2026-10-07 23:50 UTCEG score recompute
  74. 2026-10-07 23:50 UTCGHSA enrichmentGHSA-mr9v-hqxh-vq2j · GitHub severity HIGH · GitHub CVSS 7.5
  75. 2026-10-07 23:44 UTCEPSS rescoreEPSS 3.7% · 89th percentile

Frequently asked(6)

What is CVE-2020-3566?
CVE-2020-3566 is a critical-severity vulnerability; its CVE record was published on August 29, 2020. 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…
When was CVE-2020-3566 made public?
CVE-2020-3566 was made public on August 29, 2020: that is the date its CVE record's CNA, Cisco Systems, Inc., gives for when the vulnerability was made public. The CVE record itself was published on August 29, 2020. EchelonGraph's copy of the record carries a last-modified date of October 28, 2025; the record at its source may have been updated since.
Is CVE-2020-3566 actively exploited?
Yes. CISA added CVE-2020-3566 to the Known Exploited Vulnerabilities catalog on November 3, 2021, affecting Cisco IOS XR. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate attention. No fix has been recorded since the CVE record was published in 2020. Check the vendor's advisory for a fixed release; until one is applied, restrict network exposure of the affected system or apply the vendor's mitigation.
What is the CVSS score of CVE-2020-3566?
CVE-2020-3566 has a CVSS v3 base score of 8.6 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0 (CRITICAL).
Which products are affected by CVE-2020-3566?
CVE-2020-3566 affects Cisco IOS XR.
How do I remediate CVE-2020-3566?
No fix for CVE-2020-3566 has been recorded since its CVE record was published in 2020. Restrict network exposure of the affected system or apply the vendor's mitigation — for example, keep it off the internet or limit it to trusted networks — and check the vendor's advisory for a fix.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2020-3566

Explore →

Is Your Infrastructure Affected by CVE-2020-3566?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.