Security readout for executives and security teams
Plain-English summary
This flaw can make Cisco NX-OS network devices reload, causing a denial-of-service outage. It is serious because affected routers or switches may lose availability, but exploitation requires traffic that appears to come from a trusted BGP peer, not just any internet host.
Executive priority
Treat this as a high-priority network availability risk for environments using Cisco NX-OS and BGP MVPN. Prioritize validation on routing infrastructure supporting critical connectivity, because successful exploitation can force device reloads and disrupt service.
Technical view
CVE-2020-3397 is incomplete input validation in Cisco NX-OS BGP Multicast VPN handling. A specific valid BGP MVPN update message can restart BGP-related routing applications repeatedly, leading to a system-level restart. CVSS is 8.6 high with availability impact only.
Likely exposure
Exposure is most likely in Cisco NX-OS environments using BGP MVPN with explicitly configured BGP peers. The bundle does not provide exact affected versions, so teams must map their NX-OS releases and BGP MVPN use against Cisco guidance.
Exploitation context
The source says BGP accepts incoming traffic only from explicitly configured peers. An attacker must use an established TCP connection that appears to come from a trusted BGP peer and know peer details. The bundle does not show KEV listing or active exploitation evidence.
Researcher notes
The core weakness is CWE-20 input validation in BGP MVPN update processing. The public bundle gives exploit preconditions and impact, but not exact affected release ranges. Avoid assuming broader Cisco product exposure beyond NX-OS Software.
Mitigation direction
- Review Cisco’s advisory for affected and fixed NX-OS releases.
- Upgrade or patch according to Cisco’s published guidance.
- Restrict BGP peering to expected trusted network paths.
- Review BGP peer configuration for unnecessary or stale peers.
- Monitor routing process restarts and unexpected device reloads.
Validation and detection
- Inventory Cisco NX-OS devices and running software releases.
- Identify devices with BGP MVPN enabled or configured.
- Confirm all BGP peers are explicitly authorized and expected.
- Check logs for repeated BGP application restarts or reloads.
- Compare device versions against Cisco advisory guidance.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2020-3397 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.6HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20200826 Cisco NX-OS Software Border Gateway Protocol Multicast VPN Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.