CVE-2026-20171 (GCVE-0-2026-20171)
Vulnerability from cvelistv5 – Published: 2026-05-20 16:06 – Updated: 2026-05-20 18:31
VLAI?
Title
Cisco Nexus 3000 and 9000 Series Border Gateway Protocol Denial of Service Vulnerability
Summary
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.
Severity ?
6.8 (Medium)
CWE
- CWE-670 - Always-Incorrect Control Flow Implementation
Assigner
References
1 reference
Impacted products
1 product
| Vendor | Product | Version | |
|---|---|---|---|
| Cisco | Cisco NX-OS Software |
Affected:
10.2(1)
Affected: 10.2(1q) Affected: 10.2(2) Affected: 10.2(3) Affected: 10.2(3t) Affected: 10.2(2a) Affected: 10.3(1) Affected: 10.2(4) Affected: 10.3(2) Affected: 10.3(3) Affected: 10.2(5) Affected: 10.2(3v) Affected: 10.4(1) Affected: 10.3(99w) Affected: 10.2(6) Affected: 10.3(3w) Affected: 10.3(99x) Affected: 10.3(3o) Affected: 10.3(4) Affected: 10.3(3p) Affected: 10.3(4a) Affected: 10.4(2) Affected: 10.3(3q) Affected: 10.3(5) Affected: 10.2(7) Affected: 10.4(3) Affected: 10.3(3x) Affected: 10.3(4g) Affected: 10.5(1) Affected: 10.2(8) Affected: 10.3(3r) Affected: 10.3(6) Affected: 10.4(4) Affected: 10.3(4h) Affected: 10.5(2) Affected: 10.3(7) Affected: 10.4(5) Affected: 10.5(3) Affected: 10.2(9) Affected: 10.4(4g) Affected: 10.6(1) Affected: 10.5(3t) Affected: 10.3(8) Affected: 10.4(6) Affected: 10.5(3s) Affected: 10.5(3e) Affected: 10.5(3o) Affected: 10.6(1s) Affected: 10.5(3p) |
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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