# What is CVE-2019-6856?

> CVE-2019-6856 is a high-severity flaw (CVSS 7.5) in Modicon M340 from Schneider-Electric, published on 6 January 2020. 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 1.6%. If you run an affected version, plan in the vendor’s fix.

Canonical page: https://www.precursorintelligence.com/what-is/cve-2019-6856

## 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 7.5 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:** 1.6% (latest exploit-likelihood forecast)
- **Published:** 6 January 2020
- **Record last updated:** 3 February 2022
- **Main product:** Modicon M340 from Schneider-Electric
- **Affected products:** 58

## What is CVE-2019-6856? 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 CWE-754: Improper Check for Unusual or Exceptional Conditions vulnerability exists in Modicon M580, Modicon M340, Modicon Quantum, Modicon Premium (see security notification for specific versions) which could cause a Denial of Service when writing specific physical memory blocks using Modbus TCP.

### What kind of flaw is it?

- CWE-754: Improper Check for Unusual or Exceptional Conditions

### 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:U/C:N/I:N/A:H`

## Is CVE-2019-6856 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 1.6%. That can change at any time, which is why we keep watching.

Exploit likelihood over the last 7 days: 1.6%, 1.6%, 1.6%, 1.6%, 1.6%, 1.6%, 1.6%.

### Timeline

- 6 January 2020: Published
- 3 February 2022: Record last updated

### How Precursor Intelligence ranks it

CVE-2019-6856 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-2019-6856?

The published record lists 58 products. Versions are as published: "before 3.52" means every version up to, but not including, 3.52.

- [Modicon M340](https://www.precursorintelligence.com/product/schneider-electric/modicon_m340) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu65150](https://www.precursorintelligence.com/product/schneider-electric/140cpu65150) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu65150 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu65150_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu65160](https://www.precursorintelligence.com/product/schneider-electric/140cpu65160) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu65160 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu65160_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu65160s](https://www.precursorintelligence.com/product/schneider-electric/140cpu65160s) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu65160s Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu65160s_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu65260](https://www.precursorintelligence.com/product/schneider-electric/140cpu65260) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu65260 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu65260_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu65860](https://www.precursorintelligence.com/product/schneider-electric/140cpu65860) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu65860 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu65860_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu67060](https://www.precursorintelligence.com/product/schneider-electric/140cpu67060) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu67060 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu67060_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu67160](https://www.precursorintelligence.com/product/schneider-electric/140cpu67160) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu67160 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu67160_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu67160s](https://www.precursorintelligence.com/product/schneider-electric/140cpu67160s) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu67160s Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu67160s_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu67260](https://www.precursorintelligence.com/product/schneider-electric/140cpu67260) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu67260 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu67260_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu67261](https://www.precursorintelligence.com/product/schneider-electric/140cpu67261) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu67261 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu67261_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [140cpu67861](https://www.precursorintelligence.com/product/schneider-electric/140cpu67861) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [140cpu67861 Firmware](https://www.precursorintelligence.com/product/schneider-electric/140cpu67861_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.52
- [Modicon M340 Firmware](https://www.precursorintelligence.com/product/schneider-electric/modicon_m340_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.01
- [Modicon M580](https://www.precursorintelligence.com/product/schneider-electric/modicon_m580) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Modicon M580 Firmware](https://www.precursorintelligence.com/product/schneider-electric/modicon_m580_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 2.80
- [Tsxh5724m](https://www.precursorintelligence.com/product/schneider-electric/tsxh5724m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxh5724m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxh5724m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxh5744m](https://www.precursorintelligence.com/product/schneider-electric/tsxh5744m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxh5744m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxh5744m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57104m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57104m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57104m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57104m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57154m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57154m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57154m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57154m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp571634m](https://www.precursorintelligence.com/product/schneider-electric/tsxp571634m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp571634m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp571634m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57204m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57204m_) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57204m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57204m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57254m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57254m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57254m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57254m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp572634m](https://www.precursorintelligence.com/product/schneider-electric/tsxp572634m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp572634m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp572634m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57304m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57304m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57304m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57304m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57354m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57354m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57354m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57354m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp573634m](https://www.precursorintelligence.com/product/schneider-electric/tsxp573634m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp573634m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp573634m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57454m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57454m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57454m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57454m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp574634m](https://www.precursorintelligence.com/product/schneider-electric/tsxp574634m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp574634m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp574634m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp57554m](https://www.precursorintelligence.com/product/schneider-electric/tsxp57554m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp57554m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp57554m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp575634m](https://www.precursorintelligence.com/product/schneider-electric/tsxp575634m) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp575634m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp575634m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20
- [Tsxp576634m](https://www.precursorintelligence.com/product/schneider-electric/tsxp576634m_) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Hardware): version not specified
- [Tsxp576634m Firmware](https://www.precursorintelligence.com/product/schneider-electric/tsxp576634m_firmware) by [Schneider-Electric](https://www.precursorintelligence.com/vendors/schneider-electric) (Operating system): before 3.20

## How do I fix CVE-2019-6856?

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

- [se.com](https://www.se.com/ww/en/download/document/SEVD-2019-344-01) (Vendor advisory)
- [us-cert.gov](https://www.us-cert.gov/ics/advisories/icsa-20-016-01) (Third-party advisory, Government resource)

## Questions

### What is CVE-2019-6856?

CVE-2019-6856 is a high-severity flaw in Modicon M340 from Schneider-Electric, published on 6 January 2020. 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-2019-6856?

It scores 7.5 out of 10 on the CVSS severity scale, which is high. Our risk score for CVE-2019-6856 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-2019-6856 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 1.6%. That can change at any time, which is why we keep watching.

### Which versions does CVE-2019-6856 affect?

For Modicon M340 from Schneider-Electric: version not specified. The record lists 58 products in all, each with its versions, under "Who is affected" on this page.

### How do I fix CVE-2019-6856?

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-2019-6856 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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