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Full vulnerability report · 2020
CVE-2020-3566High confidence

Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Cisco · IOS XR

Official source article: Cisco CISCO-SA-IOSXR-DVMRP-MEMEXH-DSMPDVFZ ↗. Check the applicable product and release in the original source.

8.6HighCVSS 3.1
Recommended action
Protect now

CISA confirms exploitation in the wild and lists 2022-05-03 as the remediation due date.

Fix not verified
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:Critical, raised one band.upgradedsince 3 Nov 2021

Evidence used

  • CISA confirms exploitation in the wild.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 3.70% for the current model date.

Compensating controls

  • Restrict the affected network interface to trusted sources where business-safe.
  • Increase monitoring for the attack path and post-exploitation behaviour described in the report.

Verification

  1. Confirm that the asset runs Cisco IOS XR and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 3 daysRemediation target: Within 90 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2020-24837

CISA KEV mirrored by ENISA

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.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 3 Nov 2021. Evidence sources: cisa_kev.
ENISA score
8.6 · CVSS 3.1
Advisory evidence
1 linked advisory record
Recommended actionProtect now

CISA confirms exploitation in the wild and lists 2022-05-03 as the remediation due date.

Fix not verified
01

What, why and how

Cisco IOS XR Distance Vector Multicast Routing Protocol (DVMRP) incorrectly handles Internet Group Management Protocol (IGMP) packets. Exploitation could allow an unauthenticated, remote attacker to immediately crash the IGMP process or make it consume available memory and eventually crash.

What

Cisco IOS XR Distance Vector Multicast Routing Protocol (DVMRP) incorrectly handles Internet Group Management Protocol (IGMP) packets. Exploitation could allow an unauthenticated, remote attacker to immediately crash the IGMP process or make it consume available memory and eventually crash.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

Cisco IOS XR Distance Vector Multicast Routing Protocol (DVMRP) incorrectly handles Internet Group Management Protocol (IGMP) packets. Exploitation could allow an unauthenticated, remote attacker to immediately crash the IGMP process or make it consume available memory and eventually crash.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2021-11-03.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Uncontrolled Resource Consumption → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-400CISA KEV
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2020-24837Known-exploited evidence recorded

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.

Official EUVD record ↗
Cyber Security Agency of Singapore · English · CSA-SB-20200902Security Bulletin 02 Sep 2020

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 02 Sep 2020, published on 2 September 2020. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2020-AVI-611Multiples vulnérabilités dans Cisco IOS XR

De multiples vulnérabilités ont été découvertes dans Cisco IOS XR. Elles permettent à un attaquant de provoquer un déni de service à distance.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2020-010523Cisco IOS XR ソフトウェアにおける制限またはスロットリング無しのリソースの割り当てに関する脆弱性

Cisco IOS XR ソフトウェアには、制限またはスロットリング無しのリソースの割り当てに関する脆弱性が存在します。

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
Cisco IOS XR Software: n/a
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 29 Aug 2020 · Last source change 21 Oct 2025, 23:35 UTC · CWE-400 · Uncontrolled Resource Consumption

CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2020-24837
Product sourceCISA KEV
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    n/a · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Cisco IOS XR Software: n/a · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
ENISA EUVD · EUVD-2020-24837↗CISA KEV record↗CVE authority or vendor reference · Cisco CISCO-SA-IOSXR-DVMRP-MEMEXH-DSMPDVFZ↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2020-3566 · cve.blacktree.nl