Security readout for executives and security teams
Plain-English summary
This issue can make a reachable endpoint behind a Cisco Nexus 9000 ACI border leaf temporarily unreachable. The problem is not data theft or code execution; it is availability loss caused by incorrect endpoint learning under specific network conditions.
Executive priority
Treat as a moderate operational availability risk for ACI environments. Prioritize validation in data centers where endpoint reachability is business-critical or where external-to-fabric traffic reaches border leaf switches.
Technical view
In Cisco Nexus 9000 Series switches running ACI mode, improper endpoint learning can create a stale Remote XR entry when traffic enters from outside the fabric and Disable Remote Endpoint Learning is enabled. If the endpoint later migrates, traffic may not reach it until relearned.
Likely exposure
Exposure appears limited to Cisco Nexus 9000 ACI deployments using border leaf designs with Disable Remote Endpoint Learning enabled. The provided bundle does not name specific affected software versions.
Exploitation context
The CVE describes unauthenticated remote denial of service under certain circumstances. CISA KEV status is false, and the provided sources do not support active exploitation claims.
Researcher notes
The key condition is stale Remote XR endpoint state after migration, not compromise of confidentiality or integrity. Provided evidence does not include fixed versions, workarounds, or exploit reports, so remediation should be tied to Cisco advisory guidance.
Mitigation direction
- Review Cisco advisory for affected releases and official remediation.
- Inventory Nexus 9000 ACI border leaf deployments.
- Confirm whether Disable Remote Endpoint Learning is enabled.
- Prioritize vendor-recommended upgrades or mitigations where applicable.
- Monitor for endpoint reachability failures after endpoint migration.
Validation and detection
- Confirm switches are Cisco Nexus 9000 running ACI mode.
- Identify border leaf switches receiving traffic from outside the fabric.
- Check whether Disable Remote Endpoint Learning is enabled.
- Review incidents where migrated endpoints became unreachable.
- Compare deployed software 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-371: 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-2019-1977 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
- Medium
- CVSS
- 6.8 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:H/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:H/PR:N/UI:N/S:C/C:N/I:N/A:H2.24Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
6.8MediumVector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20190828 Cisco Nexus 9000 Series Fabric Switches ACI Mode Border Leaf Endpoint Learning 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.
State Issues
State Issues represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.