# What is CVE-2019-1873?

> CVE-2019-1873 is a high-severity flaw (CVSS 8.6) in ASA 5506-X Firmware from Cisco, published on 10 July 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 2.5%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2019-1873

## 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:** 48 out of 100 (Medium); action: Plan remediation. Kept up to date as the evidence changes.
- **Severity:** High (CVSS 8.6 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:** 2.5% (latest exploit-likelihood forecast)
- **Published:** 10 July 2019
- **Record last updated:** 16 October 2020
- **Main product:** ASA 5506-X Firmware from Cisco
- **Affected products:** 10

## What is CVE-2019-1873? 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 take it offline.

### The official description

A vulnerability in the cryptographic driver for Cisco Adaptive Security Appliance Software (ASA) and Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause the device to reboot unexpectedly. The vulnerability is due to incomplete input validation of a Secure Sockets Layer (SSL) or Transport Layer Security (TLS) ingress packet header. An attacker could exploit this vulnerability by sending a crafted TLS/SSL packet to an interface on the targeted device. An exploit could allow the attacker to cause the device to reload, which will result in a denial of service (DoS) condition. Note: Only traffic directed to the affected system can be used to exploit this vulnerability. This vulnerability affects systems configured in routed and transparent firewall mode and in single or multiple context mode. This vulnerability can be triggered by IPv4 and IPv6 traffic. A valid SSL or TLS session is required to exploit this vulnerability.

### What kind of flaw is it?

- CWE-20: Improper Input Validation
- CWE-400: Uncontrolled Resource Consumption

### 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 take it offline

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

## Is CVE-2019-1873 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 2.5%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 2.5%, 2.5%, 2.5%, 2.5%, 2.5%, 2.5%, 2.5%.

### Timeline

- 10 July 2019: Published
- 16 October 2020: Record last updated

### How Precursor Intelligence ranks it

CVE-2019-1873 scores **48 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-2019-1873?

The published record lists 10 products.

- [ASA 5506-X Firmware](https://www.precursorintelligence.com/product/cisco/asa_5506-x_firmware) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): 9.6(4.16), 9.8(3.8)
- [ASA 5506h-X Firmware](https://www.precursorintelligence.com/product/cisco/asa_5506h-x_firmware) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): 9.6(4.16), 9.8(3.8)
- [ASA 5506w-X Firmware](https://www.precursorintelligence.com/product/cisco/asa_5506w-x_firmware) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): 9.6(4.16), 9.8(3.8)
- [ASA 5508-X Firmware](https://www.precursorintelligence.com/product/cisco/asa_5508-x_firmware) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): 9.6(4.16), 9.8(3.8)
- [ASA 5516-X Firmware](https://www.precursorintelligence.com/product/cisco/asa_5516-x_firmware) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Operating system): 9.6(4.16), 9.8(3.8)
- [ASA 5506-X](https://www.precursorintelligence.com/product/cisco/asa_5506-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [ASA 5506h-X](https://www.precursorintelligence.com/product/cisco/asa_5506h-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [ASA 5506w-X](https://www.precursorintelligence.com/product/cisco/asa_5506w-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [ASA 5508-X](https://www.precursorintelligence.com/product/cisco/asa_5508-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified
- [ASA 5516-X](https://www.precursorintelligence.com/product/cisco/asa_5516-x) by [Cisco](https://www.precursorintelligence.com/vendors/cisco) (Hardware): version not specified

## How do I fix CVE-2019-1873?

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-20190710-asa-ftd-dos) (Vendor advisory)
- [securityfocus.com](http://www.securityfocus.com/bid/109123) (Third-party advisory, Vulnerability database)

## Questions

### What is CVE-2019-1873?

CVE-2019-1873 is a high-severity flaw in ASA 5506-X Firmware from Cisco, published on 10 July 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 take it offline.

### How serious is CVE-2019-1873?

It scores 8.6 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2019-1873 is 48 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-2019-1873 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 2.5%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2019-1873 affect?

For ASA 5506-X Firmware from Cisco: 9.6(4.16), 9.8(3.8). The record lists 10 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2019-1873?

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-2019-1873 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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