How severe is CVE-2021-1586?

CVE-2021-1586 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-1586 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-1586?

CVE-2021-1586 primarily affects Cisco Nx-os. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-1586?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2021-1586 published?

CVE-2021-1586 was published on 2021-08-25 and last updated on 2026-06-17.

CVE-2021-1586

CVE-2021-1586 is a high-severity vulnerability in Cisco Nx-os with a CVSS 3.x base score of 8.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-345.

Key facts

Severity: High (CVSS 3.x base score 8.6)
CVSS v2: 5.0
EPSS exploit prediction: 2% (82nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-345
Affected product: Cisco Nx-os
Published: 2021-08-25
Last modified: 2026-06-17

Description

A vulnerability in the Multi-Pod or Multi-Site network configurations for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to unexpectedly restart the device, resulting in a denial of service (DoS) condition. This vulnerability exists because TCP traffic sent to a specific port on an affected device is not properly sanitized. An attacker could exploit this vulnerability by sending crafted TCP data to a specific port that is listening on a public-facing IP address for the Multi-Pod or Multi-Site configuration. A successful exploit could allow the attacker to cause the device to restart unexpectedly, resulting in a DoS condition.

Frequently asked questions

What is CVE-2021-1586?: A vulnerability in the Multi-Pod or Multi-Site network configurations for Cisco Nexus 9000 Series Fabric Switches in Application Centric Infrastructure (ACI) mode could allow an unauthenticated, remote attacker to unexpectedly restart the device, resulting in a denial of service (DoS) condition. This vulnerability exists because TCP traffic sent to a specific port on an affected device is not properly sanitized. An attacker could exploit this vulnerability by sending crafted TCP data to a specific port that is listening on a public-facing IP address for the Multi-Pod or Multi-Site configuration. A successful exploit could allow the attacker to cause the device to restart unexpectedly, resulting in a DoS condition.
How severe is CVE-2021-1586?: CVE-2021-1586 has a CVSS 3.x base score of 8.6, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-1586 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (82nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-1586?: CVE-2021-1586 primarily affects Cisco Nx-os. In total, 2 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-1586?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.
When was CVE-2021-1586 published?: CVE-2021-1586 was published on 2021-08-25 and last updated on 2026-06-17.

References

https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-n9kaci-tcp-dos-YXukt6gM

Affected products (2)

cpe:2.3:o:cisco:nx-os:15.0\(2e\):*:*:*:*:*:*:*
cpe:2.3:o:cisco:nx-os:15.1\(1h\):*:*:*:*:*:*:*

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