Security readout for executives and security teams
Plain-English summary
Cisco NX-OS devices using BGP Multicast VPN can mishandle a valid BGP update and repeatedly reset BGP sessions. That can destabilize routes and disrupt traffic. The attacker must appear as a trusted BGP peer, so exposure is concentrated in routed network cores and provider-style environments.
Executive priority
Treat as high priority for networks where NX-OS participates in BGP MVPN routing. The business risk is traffic disruption from unstable routing, not data theft. Urgency depends on whether affected routing features are deployed in production.
Technical view
CVE-2020-3398 is an NX-OS BGP MVPN parsing flaw, classified as CWE-20. A crafted but valid MVPN update over an established peer connection can cause corrupted BGP updates and repeated peer resets, creating partial denial of service through routing instability.
Likely exposure
Exposure is likely limited to Cisco NX-OS deployments with BGP MVPN enabled and explicitly configured BGP peers. The bundle does not provide affected version ranges, so teams must confirm platforms and releases against Cisco guidance.
Exploitation context
The CVE is not listed as KEV in the supplied bundle, and no source here states active exploitation. Exploitation requires network reachability as an established trusted BGP peer and knowledge of peer details.
Researcher notes
The supplied evidence identifies incorrect parsing of a specific BGP MVPN update. It does not provide exploit code, affected version ranges, or named fixes. Validation should focus on feature exposure, trusted peer boundaries, and observed BGP session resets.
Mitigation direction
- Check Cisco advisory for affected platforms, fixed releases, and workarounds.
- Prioritize NX-OS systems running BGP MVPN in critical routing paths.
- Apply Cisco-provided software updates or mitigations where applicable.
- Restrict BGP peering to expected neighbors and trusted transport paths.
- Monitor for repeated BGP resets and route instability.
Validation and detection
- Inventory Cisco NX-OS devices with BGP MVPN configured.
- Compare device releases and platforms with Cisco advisory details.
- Review BGP peer reset history for repeated unexplained flaps.
- Confirm peers are explicitly configured and expected.
- Assess business impact of route instability on critical services.
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-2020-3398 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 Session 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.