Cisco Nexus 9000 Series Fabric Switches ACI Mode Border Leaf Endpoint Learning Vulnerability
Priority LOW 36CWE-371Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Fixed
Attack profile from CVSS 3.0 · NVD. Fix status from CNA.
Summary
A vulnerability within the Endpoint Learning feature of Cisco Nexus 9000 Series Switches running in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an endpoint device in certain circumstances. The vulnerability is due to improper endpoint learning when packets are received on a specific port from outside the ACI fabric and destined to an endpoint located on a border leaf when Disable Remote Endpoint Learning has been enabled. This can result in a Remote (XR) entry being created for the impacted endpoint that will become stale if the endpoint migrates to a different port or leaf switch. This results in traffic not reaching the impacted endpoint until the Remote entry can be relearned by another mechanism.
Why it matters now
Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.01495 74th percentileScored 2026-11-07
Fix Fixed Cisco Nexus 9000 Series Fabric Switches in ACI (Cisco): 12.2(4M)
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- No
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Cisco | Cisco Nexus 9000 Series Fabric Switches in ACI | before 12.2(4M) | 12.2(4M) | Patch available | CNA |
- Cisco Nexus 9000 Series Fabric Switches in ACI VendorCisco Affected before 12.2(4M) Fixed in 12.2(4M) Patch available CNA
CPE configurations NVD · 26
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:cisco:nx-os:12.3\(1h\):*:*:*:*:*:*:* | 12.3(1h) | Vulnerable | Cisco |
| cpe:2.3:o:cisco:nx-os:13.1\(2m\):*:*:*:*:*:*:* | 13.1(2m) | Vulnerable | Cisco |
| cpe:2.3:o:cisco:nx-os:13.1\(2o\):*:*:*:*:*:*:* | 13.1(2o) | Vulnerable | Cisco |
| cpe:2.3:o:cisco:nx-os:13.1\(2p\):*:*:*:*:*:*:* | 13.1(2p) | Vulnerable | Cisco |
| cpe:2.3:h:cisco:nexus_9000:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_93108tc-ex:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_93108tc-fx:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_93120tx:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_93128tx:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_93180lc-ex:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
- cpe:2.3:o:cisco:nx-os:12.3\(1h\):*:*:*:*:*:*:* Versions 12.3(1h) Vulnerable ·Cisco
- cpe:2.3:o:cisco:nx-os:13.1\(2m\):*:*:*:*:*:*:* Versions 13.1(2m) Vulnerable ·Cisco
- cpe:2.3:o:cisco:nx-os:13.1\(2o\):*:*:*:*:*:*:* Versions 13.1(2o) Vulnerable ·Cisco
- cpe:2.3:o:cisco:nx-os:13.1\(2p\):*:*:*:*:*:*:* Versions 13.1(2p) Vulnerable ·Cisco
- cpe:2.3:h:cisco:nexus_9000:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_93108tc-ex:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_93108tc-fx:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_93120tx:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_93128tx:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_93180lc-ex:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
Show 16 more CPE
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:h:cisco:nexus_93180yc-ex:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_93180yc-fx:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9332pq:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9336c-fx2:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9336pq:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9348gc-fxp:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9364c:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9372px:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9372px-e:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9372tx:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9372tx-e:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9396px:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9396tx:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9504:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9508:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:nexus_9516:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
- cpe:2.3:h:cisco:nexus_93180yc-ex:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_93180yc-fx:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9332pq:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9336c-fx2:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9336pq:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9348gc-fxp:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9364c:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9372px:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9372px-e:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9372tx:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9372tx-e:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9396px:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9396tx:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9504:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9508:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:nexus_9516:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
Remediation
- Fix · CNA Cisco Nexus 9000 Series Fabric Switches in ACI (Cisco) Fixed in 12.2(4M)
Timeline
- 2026-10-02 Threatist record created from CVE-2019-1977
- 2026-10-03 Alias added: GHSA-3993-q22g-mw33
References
More Cisco Nx-os vulnerabilities
- TI-2023-23979 The HTTP/2 protocol allows a denial of service (server resource consumption) because… KEVCVSS 3.1HIGH 7.5
- TI-2024-13332 Cisco NX-OS Software CLI Command Injection Vulnerability KEVCVSS 3.1MEDIUM 6.7
- TI-2018-00260 Improper input validation in Cisco NX-OS unknown CVSS 3.0CRITICAL 9.8
- TI-2019-01226 Cisco NX-OS Software Netstack Denial of Service Vulnerability CVSS 3.1HIGH 8.6
- TI-2022-05183 Cisco NX-OS Software Cisco Fabric Services Over IP Denial of Service Vulnerability CVSS 3.1HIGH 8.6
- TI-2022-05182 Cisco Nexus 9000 Series Switches Bidirectional Forwarding Detection Denial of Service Vulnerability CVSS 3.1HIGH 8.6
Sources
- CVE-2019-1977 · CVE Program
- CVE-2019-1977 · NVD
- FIRST EPSS
- GHSA-3993-q22g-mw33 · GitHub Advisory Database · CC BY 4.0
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