---
id: CVE-2020-22552
title: >-
  The Snap7 server component in version 1.4.1, when an attacker sends a crafted
  packet with COTP protocol the last-data-unit flag set to No and S7 writes a
  var function, the Snap7 server will be crashed.
summary: >-
  The Snap7 server component in version 1.4.1, when an attacker sends a crafted
  packet with COTP protocol the last-data-unit flag set to No and S7 writes a
  var function, the Snap7 server will be crashed.
severity: high
cvss: 7.5
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H'
vendor: snap7_project
product: snap7
affected:
  - snap7 = 1.4.1
published: '2020-10-28'
updated: '2026-07-05'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2020-22552'
references:
  - url: 'https://sourceforge.net/p/snap7/discussion/bugfix/thread/456d76fdde/'
    label: cve@mitre.org
  - url: 'https://sourceforge.net/projects/snap7/'
    label: cve@mitre.org
  - url: 'http://snap7.com'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://sourceforge.net/p/snap7/discussion/bugfix/thread/456d76fdde/'
    label: af854a3a-2127-422b-91ae-364da2661108
  - url: 'https://sourceforge.net/projects/snap7/'
    label: af854a3a-2127-422b-91ae-364da2661108
tags:
  - nvd
epss: 0.01473
epssPercentile: 0.72676
ingestedAt: '2026-07-05T00:59:25.503Z'
---

## Overview

The Snap7 server component in version 1.4.1, when an attacker sends a crafted packet with COTP protocol the last-data-unit flag set to No and S7 writes a var function, the Snap7 server will be crashed.

## Affected

- `snap7 = 1.4.1`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.