CVE-2026-20171

MEDIUM

A vulnerability in the Border Gateway Protocol (BGP) enforce-first-as feature of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow...

Affects 0 products across 7 vendors.

BCS4.29
CVSS 3.16.8
EPSS0.5%
Percentile38th
PatchUnknown
CVSS Vector — Plain English Remotely exploitable over the network, high complexity, no authentication required, no user interaction needed, can impact systems beyond the vulnerable component, no confidentiality impact, no integrity impact, full availability impact.
CWE Weakness Definitions
CWE-670: CWE-670
◆ SAGE Intelligence — CITED Relevance Research Team

A vulnerability in the Border Gateway Protocol (BGP) enforce-first-as feature of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition.

BSID: BS-2026-GLOBAL-063241-M • Model: /workspace/models/qwen2.5-coder-32b-instruct-bf16 • Confidence: MEDIUM

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Frequently Asked Questions
What is CVE-2026-20171?
A vulnerability in the Border Gateway Protocol (BGP) enforce-first-as feature of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition.
What is the CVSS score for CVE-2026-20171?
CVE-2026-20171 has CVSS 6.8 (Medium). Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H. EPSS: 0.5%.
Is CVE-2026-20171 actively exploited?
No confirmed active exploitation of CVE-2026-20171 as of 2026-07-24.
How do I remediate CVE-2026-20171?
Priority: MEDIUM. Advisory: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-bgp-iefab-3hb2pwtx PSIRT: [email protected]
What systems are affected by CVE-2026-20171?
CVE-2026-20171 affects: Cisco, Enforce, Flap, Francisco Burzi, Gateway, Nexus, Protocol.
Vulnerability Details
CVE IDCVE-2026-20171
BSIDBS-2026-GLOBAL-063241-M BreachSpider Global ID
CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:H
Published2026-05-20
Last Modified2026-07-23
ICS Relevance55%
Weakness (CWE)
CWE-670
Domains
NETWORK-INFRA
SourceNVD
Official Description

A vulnerability in the Border Gateway Protocol (BGP) enforce-first-as feature of Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, remote attacker to trigger BGP peer flaps, resulting in a denial of service (DoS) condition. This vulnerability is due to incorrect parsing of a transitive BGP attribute. An attacker could exploit this vulnerability by sending a crafted BGP update through an established BGP peer session. If the update propagates to an affected device, it could cause the device to drop the BGP session and flap with the BGP peer that is forwarding this update, resulting in a DoS condition.

Source: NIST NVD / MITRE CVE Database

Attack Vector Analysis — CITED Relevance

The vulnerability is due to incorrect parsing of a transitive BGP attribute, which could be exploited by an unauthenticated, remote attacker to cause BGP peer flaps.

Exploitation Likelihood: MEDIUM

Affected Products
VendorProductFixed Version
Cisco — —
Enforce — —
Flap — —
Francisco Burzi — —
Gateway — —
Nexus — —
Protocol — —
Remediation
View Vendor Advisory →

Remediation Priority: MEDIUM

Vendor PSIRT: [email protected]
Threat Intelligence
● Threat Intelligence Validated: July 2026 | Threat Age: 66 Days
CISA KEVNot in KEV catalog
Public ExploitNot confirmed
PoC CodeNot confirmed
SAGE Enrichment Record — provenance & audit hash
Model/workspace/models/qwen2.5-coder-32b-instruct-bf16
ConfidenceMEDIUM
Enriched At2026-05-24
SHA-512 Audit Hash1dcb1ffe636b7947664520e11c6be2ba68a9b5a83c06cb977559017ca24f4a7f80f5480abbdfdf54b9fcf4a399b4c4dcac2300c480def867d1b124a26010babc
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