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PatchSiren cyber security CVE debrief

CVE-2020-3566 Cisco CVE debrief

CVE-2020-3566 is a Cisco IOS XR Software DVMRP memory exhaustion vulnerability that CISA has listed in the Known Exploited Vulnerabilities catalog. For defenders, the key takeaway is simple: this issue has been publicly identified as known exploited, so IOS XR environments should be reviewed and updated using Cisco’s guidance as soon as possible.

Vendor
Cisco
Product
IOS XR
CVSS
HIGH 8.6
CISA KEV
Listed
Original CVE published
2021-11-03
Original CVE updated
2021-11-03
Advisory published
2021-11-03
Advisory updated
2021-11-03

Who should care

Cisco IOS XR administrators, network security teams, and incident responders responsible for perimeter and core routing infrastructure should prioritize this CVE, especially any environment running DVMRP-related functionality.

Technical summary

The official records in this corpus identify the issue as a memory exhaustion vulnerability in Cisco IOS XR Software’s DVMRP handling. CISA’s KEV entry confirms the vulnerability is known exploited and directs organizations to apply updates per vendor instructions. No additional impact details are included in the supplied source corpus, so validation should rely on the official Cisco and NVD/CVE records linked here.

Defensive priority

High. CISA lists CVE-2020-3566 in KEV, which makes it a priority for patching and exposure review in Cisco IOS XR deployments.

Recommended defensive actions

  • Check whether any Cisco IOS XR systems use DVMRP-related functionality or are otherwise exposed to the affected code path.
  • Review the Cisco advisory and related vendor update guidance referenced by the official records.
  • Apply Cisco-provided updates or mitigations as directed by the vendor.
  • Verify remediation across all IOS XR assets rather than a single device or site.
  • Monitor Cisco IOS XR systems for unusual resource exhaustion or instability until remediation is complete.

Evidence notes

This debrief is based only on the supplied official corpus: the CISA KEV source item, the CVE.org record link, and the NVD detail link. The corpus confirms the vulnerability name, product, KEV status, date added (2021-11-03), and due date (2022-05-03). It does not provide version ranges, exploit mechanics, or broader impact details, so those are intentionally not inferred here.

Sources and references

Verified primary and authoritative sources

  • CVE-2020-3566 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2020-3566

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2020-3566 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2020-3566

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

  • CISA Known Exploited Vulnerabilities catalog

    Publisher, destination, and source semantics verified

    URL: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

    Cybersecurity and Infrastructure Security Agency - Official CISA catalog of vulnerabilities known to be exploited in the wild.

Supplemental references

  • Source item URL

    Unverified legacy reference

    URL: https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

    cisa_kev

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.