# What is CVE-2019-12643?

> CVE-2019-12643 is a critical-severity flaw (CVSS 10.0) in IOS XE from Cisco, published on 28 August 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 5.3%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2019-12643

## At a glance

- **Verdict:** Fix this soon. Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.
- **Precursor Intelligence risk score:** 55 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** Critical (CVSS 10.0 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:** 5.3% (latest exploit-likelihood forecast)
- **Published:** 28 August 2019
- **Record last updated:** 9 October 2019
- **Main product:** IOS XE from Cisco
- **Affected products:** 8

## What is CVE-2019-12643? In plain terms

It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### The official description

A vulnerability in the Cisco REST API virtual service container for Cisco IOS XE Software could allow an unauthenticated, remote attacker to bypass authentication on the managed Cisco IOS XE device. The vulnerability is due to an improper check performed by the area of code that manages the REST API authentication service. An attacker could exploit this vulnerability by submitting malicious HTTP requests to the targeted device. A successful exploit could allow the attacker to obtain the token-id of an authenticated user. This token-id could be used to bypass authentication and execute privileged actions through the interface of the REST API virtual service container on the affected Cisco IOS XE device. The REST API interface is not enabled by default and must be installed and activated separately on IOS XE devices. See the Details section for more information.

### What kind of flaw is it?

- CWE-287: Improper Authentication

### How an attack on it works

- Where an attacker can be: Anywhere on the internet
- 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 read data, change data and take it offline

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

## Is CVE-2019-12643 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 5.3%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 5.3%, 5.3%, 5.3%, 5.3%, 5.3%, 5.3%, 5.3%.

### Timeline

- 28 August 2019: Published
- 9 October 2019: Record last updated
- 19 November 2025: Exploit likelihood jumped
- 22 November 2025: Exploit likelihood fell

### How Precursor Intelligence ranks it

CVE-2019-12643 scores **55 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-2019-12643?

The published record lists 8 products.

- [IOS XE](https://www.precursorintelligence.com/product/cisco/ios_xe) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): 15.5(3)s3.16, 16.6.5
- [4221 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4221_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [4321 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4321_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [4331 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4331_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [4351 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4351_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [4431 Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4431_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [4451-X Integrated Services Router](https://www.precursorintelligence.com/product/cisco/4451-x_integrated_services_router) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [Cloud Services Router 1000v](https://www.precursorintelligence.com/product/cisco/cloud_services_router_1000v) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified

## How do I fix CVE-2019-12643?

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-20190828-iosxe-rest-auth-bypass) (Vendor advisory)

## Questions

### What is CVE-2019-12643?

CVE-2019-12643 is a critical-severity flaw in IOS XE from Cisco, published on 28 August 2019. It can be attacked from anywhere on the internet without logging in, and nobody has to click anything. If it works, the attacker can read data, change data and take it offline.

### How serious is CVE-2019-12643?

It scores 10.0 out of 10 on the CVSS severity scale, which is critical. Our risk score for CVE-2019-12643 is 55 out of 100, which is Medium. Its action is "Plan remediation". Not confirmed as exploited yet, but serious or likely enough that it should not wait for a quiet month.

### Is CVE-2019-12643 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 5.3%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2019-12643 affect?

For IOS XE from Cisco: 15.5(3)s3.16, 16.6.5. The record lists 8 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2019-12643?

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-2019-12643 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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