Critical Memory Exhaustion Vulnerability in Cisco IOS XR DVMRP (CVE‑2020‑3566) Threatens Network Service Availability
What It Is – Cisco IOS XR’s implementation of the Distance Vector Multicast Routing Protocol (DVMRP) mishandles IGMP packets, allowing an unauthenticated remote attacker to trigger memory exhaustion. The flaw can crash the IGMP process or consume all available memory, leading to a denial‑of‑service condition.
Exploitability – Remote, unauthenticated exploitation is publicly known; a proof‑of‑concept exists. CVSS 3.1 base score 9.8 (Critical).
Affected Products – Cisco IOS XR software (all versions containing the vulnerable DVMRP component).
Why It Matters for Trust & Control Assurance
- Control Objective – Service Availability & Resilience: Organizations must demonstrate that critical network services remain operational, which requires timely patching and continuous monitoring of device health.
- Evidence of Due Diligence: Remediation actions (patch deployment, configuration verification) generate audit‑ready logs that satisfy multiple frameworks (e.g., NIST CSF, ISO 27001) through a single control.
- Defensible Audit Trail: Continuous evidence collection of patch status and memory‑usage metrics provides the proof points auditors expect for “availability” controls.
Recommended Actions
- Identify all Cisco IOS XR devices running DVMRP and verify the current software version.
- Apply Cisco’s security advisory patch that addresses CVE‑2020‑3566.
- Enable monitoring of IGMP process health and memory consumption; set alerts for abnormal spikes.
- Record remediation steps in your change‑management system to create immutable evidence of control execution.
- Update your asset inventory and control‑mapping repository to reflect the patched state.
Source: CISA KEV – CVE‑2020‑3566