VulnerabilityPublished 25 Feb 2026

CVE-2026-20033: Cisco NX-OS System Software in ACI Mode · Buffer Access with Incorrect Length Value

Affects Cisco NX-OS System Software in ACI ModeSource CVE Database V5

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Not known to be exploited · CVSS 7.4 High.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 3.1 base score

7.4High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.1% chance of exploitation in 30 days – higher than 6% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Attack Vector: Adjacent
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Changed
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 25 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 29 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
CiscoCisco NX-OS System Software in ACI Mode	Affected 15.2(1g) – 16.1(4h) 57 affected builds	Fixed in–

AI-suggested

To mitigate CVE-2026-20033, organizations should take the following specific actions: 1) Immediately restrict access to the out-of-band management interfaces of affected Cisco Nexus 9000 switches by implementing strict network segmentation and access control lists (ACLs) to limit connectivity only to trusted administrators and management systems. 2) Apply Cisco's security patches or software updates addressing this vulnerability as soon as they become available, ensuring that all affected NX-OS versions are upgraded to fixed releases. 3) Monitor network traffic on the OOB management network for anomalous or malformed Ethernet frames that could indicate exploitation attempts. 4) Employ network intrusion detection/prevention systems (IDS/IPS) capable of detecting suspicious frame patterns targeting the management interface. 5) Regularly audit and validate the configuration of management interfaces to ensure they are not exposed to untrusted networks or users. 6) Develop and test incident response plans to quickly recover from potential device reloads or outages caused by exploitation. 7) Consider deploying redundancy and high availability configurations to minimize impact if a device reload occurs. These targeted mitigations go beyond generic advice by focusing on protecting the specific attack vector (OOB management interface) and ensuring rapid patch deployment.

Description

A vulnerability in Cisco Nexus 9000 Series Fabric Switches in ACI mode could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to insufficient validation when processing specific Ethernet frames. An attacker could exploit this vulnerability by sending a crafted Ethernet frame to the management interface of an affected device. A successful exploit could allow the attacker to cause the device to reload unexpectedly, resulting in a DoS condition. Note: Only the out-of-band (OOB) management interface is affected.

Impact

The primary impact of CVE-2026-20033 is a denial of service condition caused by unexpected device reloads on Cisco Nexus 9000 switches operating in ACI mode. This can lead to network outages, loss of connectivity, and disruption of critical data center operations. Organizations using these switches for fabric management or as part of their core network infrastructure may experience degraded performance or complete loss of network services during an attack. The vulnerability does not allow for data confidentiality or integrity compromise directly, but the availability impact can affect business continuity, especially in environments with high uptime requirements such as financial institutions, cloud providers, and large enterprises. Additionally, repeated exploitation could increase operational costs due to troubleshooting and recovery efforts. Since the attack requires adjacency to the OOB management interface, environments with poorly segmented management networks are at higher risk. The broad range of affected software versions implies many organizations may be vulnerable if patches are not applied promptly.

References

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-nxos-cpdos-qLsv6pFD (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Feb 2026, 00:01 UTC

Technical details

References

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