# What is CVE-2019-1594?

> CVE-2019-1594 is a high-severity flaw (CVSS 7.4) in NX-OS from Cisco, published on 6 March 2019. It is not on the list of flaws known to be exploited today. The latest forecast puts its chance of use in the next 30 days at 0.8%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2019-1594

## At a glance

- **Verdict:** Plan it in. No sign of exploitation and a low forecast. Patch it in your normal update cycle.
- **Precursor Intelligence risk score:** 46 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 7.4 out of 10)
- **Known to be exploited:** No, not on the list of flaws known to be exploited today
- **Chance of use in the next 30 days:** 0.8% (latest exploit-likelihood forecast)
- **Published:** 6 March 2019
- **Record last updated:** 9 October 2019
- **Main product:** NX-OS from Cisco
- **Affected products:** 12

## What is CVE-2019-1594? In plain terms

An attacker has to be on the same local network without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### The official description

A vulnerability in the 802.1X implementation for Cisco NX-OS Software could allow an unauthenticated, adjacent attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to incomplete input validation of Extensible Authentication Protocol over LAN (EAPOL) frames. An attacker could exploit this vulnerability by sending a crafted EAPOL frame to an interface on the targeted device. A successful exploit could allow the attacker to cause the Layer 2 (L2) forwarding process to restart multiple times, leading to a system-level restart of the device and a DoS condition. Note: This vulnerability affects only NX-OS devices configured with 802.1X functionality. Cisco Nexus 1000V Switch for VMware vSphere devices are affected in versions prior to 5.2(1)SV3(1.4b). Nexus 3000 Series Switches are affected in versions prior to 7.0(3)I7(4). Nexus 3500 Platform Switches are affected in versions prior to 7.0(3)I7(4). Nexus 2000, 5500, 5600, and 6000 Series Switches are affected in versions prior to 7.3(5)N1(1) and 7.1(5)N1(1b). Nexus 7000 and 7700 Series Switches are affected in versions prior to 8.2(3). Nexus 9000 Series Fabric Switches in ACI Mode are affected in versions prior to 13.2(1l). Nexus 9000 Series Switches in Standalone NX-OS Mode are affected in versions prior to 7.0(3)I7(4).

### What kind of flaw is it?

- CWE-20: Improper Input Validation

### How an attack on it works

- Where an attacker can be: On the same local network
- How hard it is to pull off: Easy: no special conditions
- Login needed first: No login needed
- Does someone have to click: No, nobody has to do anything
- What an attacker gets: Can take it offline

Severity vector: `CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`

## Is CVE-2019-1594 being exploited? Not that we know of

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.8%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 0.8%, 0.8%, 0.8%, 0.8%, 0.8%, 0.8%, 0.8%.

### Timeline

- 6 March 2019: Published
- 9 October 2019: Record last updated

### How Precursor Intelligence ranks it

CVE-2019-1594 scores **46 out of 100 (Medium)**, with the action "Plan remediation".

Every published flaw gets a risk score from 0 to 100, kept up to date as the evidence changes. Four things go into the score, from the one that counts most to the ones that count less:

- Evidence it is being exploited: biggest factor
- How severe it is: strong factor
- How widely exposed it is: smaller factor
- Threat activity around it: smaller factor

85 and above is Critical. Anything confirmed as exploited is always marked for an emergency patch, whatever its score. When this flaw matches software you track, it lands in your list with its score and the reasons behind it.

## Who is affected by CVE-2019-1594?

The published record lists 12 products. Versions are as published: "before 5.2(1)sv3(1.4b)" means every version up to, but not including, 5.2(1)sv3(1.4b).

- [NX-OS](https://www.precursorintelligence.com/product/cisco/nx-os) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): before 5.2(1)sv3(1.4b), before 7.1(5)n1(1b), before 13.2(1l), 6.2 to before 6.2(20a), 7.0(3)i7 to before 7.0(3)i7(4), 7.2 to before 7.3(5)n1(1), 8.0 to before 8.2(3), 8.3 to before 8.3(1)
- [Nexus 1000v](https://www.precursorintelligence.com/product/cisco/nexus_1000v) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 2000](https://www.precursorintelligence.com/product/cisco/nexus_2000) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 3000](https://www.precursorintelligence.com/product/cisco/nexus_3000) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 3500](https://www.precursorintelligence.com/product/cisco/nexus_3500) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 5500](https://www.precursorintelligence.com/product/cisco/nexus_5500) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 5600](https://www.precursorintelligence.com/product/cisco/nexus_5600) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 6000](https://www.precursorintelligence.com/product/cisco/nexus_6000) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 7000](https://www.precursorintelligence.com/product/cisco/nexus_7000) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 7700](https://www.precursorintelligence.com/product/cisco/nexus_7700) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 9000](https://www.precursorintelligence.com/product/cisco/nexus_9000) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Nexus 9000 in Standalone NX-OS Mode](https://www.precursorintelligence.com/product/cisco/nexus_9000_in_standalone_nx-os_mode) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified

## How do I fix CVE-2019-1594?

1. **Check whether you run it.** Compare your versions with the affected products above. Not sure what you run? Precursor Intelligence can work it out from your public website, or you can pick it from a list.
2. **Apply the vendor’s fix.** Install the update named in the vendor’s advisory. We’ve put the advisory first in the list.
3. **If you can’t patch today.** Follow any mitigation the vendor publishes, and limit who can reach the affected system from the internet until the update is in.
4. **Keep an eye on it.** Track the product and we tell you as soon as we spot this flaw on the list of exploited flaws, or a jump in its exploit likelihood.

### References

- [tools.cisco.com](https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190306-nx-os-lan-auth) (Patch, Vendor advisory)
- [securityfocus.com](http://www.securityfocus.com/bid/107325) (Third-party advisory, Vulnerability database)

## Questions

### What is CVE-2019-1594?

CVE-2019-1594 is a high-severity flaw in NX-OS from Cisco, published on 6 March 2019. An attacker has to be on the same local network without logging in, and nobody has to click anything. If it works, the attacker can take it offline.

### How serious is CVE-2019-1594?

It scores 7.4 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2019-1594 is 46 out of 100, which is Medium. Its action is "Plan remediation". No sign of exploitation and a low forecast. Patch it in your normal update cycle.

### Is CVE-2019-1594 being exploited?

It is not on the list of flaws known to be exploited today. The latest forecast puts the chance of it being used in the next 30 days at 0.8%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2019-1594 affect?

For NX-OS from Cisco: before 5.2(1)sv3(1.4b), before 7.1(5)n1(1b), before 13.2(1l), 6.2 to before 6.2(20a), 7.0(3)i7 to before 7.0(3)i7(4), 7.2 to before 7.3(5)n1(1) and 2 more. The record lists 12 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2019-1594?

Install the update the vendor names in its advisory, linked first under "How do I fix" on this page. If you can't patch today, follow the vendor's mitigation and limit who can reach the affected system from the internet.

## Does CVE-2019-1594 affect you?

Precursor Intelligence keeps checking for you:

- **Tell us what you run.** Pick your software from a list, or let us work it out from your website.
- **We match it to every flaw.** Over 400,000 published flaws, checked against your list.
- **Ranked by real-world risk.** Every flaw gets a 0 to 100 risk score, kept up to date, led by evidence criminals are using it.
- **Told as soon as we know.** An alert by email, in the app or by webhook to your own tools.

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