CVE-2020-3566· NVD / CVE Program· CNA cisco

Cisco IOS XR Software DVMRP Memory Exhaustion Vulnerability

Noroxi assessment

Priority: This week (action score 65/100)

CISA has confirmed exploitation in the wild (Nov 3, 2021). Remediation deadline for US federal agencies: May 3, 2022.
Probability of exploitation in the next 30 days: 3.7% (FIRST EPSS); higher than 89.6% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to CISA the attack is automatable: targets can be found by mass scanning.
According to the record, no fixed version is available yet.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Don’t wait for the next maintenance window. Until a fix is released, restrict access to the affected component and follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

HighCVSS 8.6 · v3.1KEVWeaponized No fix recorded

BDU:2020-04144

Published: Aug 29, 2020
Updated: Jun 16, 2026
EPSS: 3.7% · 89th percentile
CWE: CWE-400

Report tools

JSON

Action score

This week

Don’t wait for the next maintenance window.

CVSS: 34 / 40 · 8.6 / 10
CISA KEV: 30 / 30 · Listed
EPSS: 1 / 30 · 3.7%

CISA SSVC decision

Exploitation: active
Automatable: yes
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 8.6
CNA · cisco: 8.6; agree

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Nov 3, 2021. That signals real attacks, not theory.

Remediation deadline for US federal agencies: May 3, 2022.

Get told when this record changes

In CISA KEV: exploitation in the wild confirmed
Weaponized exploit exists
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
cisco	ios xr	cpe:2.3:o:cisco:ios_xr
cisco	asr 9001	cpe:2.3:h:cisco:asr_9001
cisco	asr 9006	cpe:2.3:h:cisco:asr_9006
cisco	asr 9010	cpe:2.3:h:cisco:asr_9010
cisco	asr 9901	cpe:2.3:h:cisco:asr_9901
cisco	asr 9904	cpe:2.3:h:cisco:asr_9904
cisco	asr 9906	cpe:2.3:h:cisco:asr_9906
cisco	asr 9910	cpe:2.3:h:cisco:asr_9910
cisco	asr 9912	cpe:2.3:h:cisco:asr_9912
cisco	asr 9922	cpe:2.3:h:cisco:asr_9922

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

cisco ios xr6.4.2

Versions reported by the vendor

Affected version ranges reported by the assigning authority (cisco). Independent of NVD's CPE analysis and usually ahead of it.

Cisco Cisco IOS XR Software
- n/aaffected

Same product

cisco: all records

Other highest-scoring records for the same primary product.

CVE-2020-3118Cisco IOS XR Software Cisco Discovery Protocol Format String VulnerabilityKEV
69This week
CVE-2020-3569Cisco IOS XR Software DVMRP Memory Exhaustion VulnerabilitiesKEV
65This week
CVE-2010-3035Cisco IOS XR 3.4.0 through 3.9.1, when BGP is enabled, does not properly handle unrecognized transitive attributes, which allows remote attaKEV
62This week

Published before and after this one in the same product

← EarlierCVE-2020-3364Jun 17, 2020 · Cisco IOS XR Software Standby Route Processor Gigabit Ethernet Management Interface Access Control List Bypass Vulnerability
21Monitor
← EarlierCVE-2020-3449Aug 17, 2020 · Cisco IOS XR Software Additional Paths Denial of Service Vulnerability
17Monitor
Later →CVE-2020-3473Sep 3, 2020 · Cisco IOS XR Software Authenticated User Privilege Escalation Vulnerability
31Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

PublishedAug 29, 2020
CISA KEVNov 3, 2021+430 d
TodayOct 24, 2026+2247 d

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-20-664 · Sep 1, 2020(Cisco IOS DVMRP Zafiyeti)

All national notices →

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Impact can extend beyond the vulnerable component (scope changes).

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: None
Scope: Changed
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

nvd-primary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

No changes recorded on tracked fields yet. Score, KEV, exploit maturity and fix status changes appear here.

References

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-iosxr-dvmrp-memexh-dSmpdvfz

Show all references (1 more)

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

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records