# CVE-2020-22552: Denial of service in n/a

> A crafted packet with specific COTP flags causes the Snap7 server to crash, resulting in a denial of service.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Oct 2020
- **Updated:** 9 Jul 2026
- **Also known as:** GHSA-c87p-2q2j-cwwp

## What is CVE-2020-22552?

CVE-2020-22552 is a high-severity denial of service vulnerability in n/a, published on 28 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

## Which versions are affected by CVE-2020-22552?

It affects 1 product.


Products: Snap7 Project Snap7.

## How do I fix CVE-2020-22552?

No fix has been published for CVE-2020-22552 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-22552 being exploited?

There is no known exploitation of CVE-2020-22552 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-22552 and fix it if it is affected.

What it is: CVE-2020-22552 is a high-severity denial of service vulnerability in n/a, published on 28 Oct 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-22552 in the wild and no public exploit code.

Affected product: n/a. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2020-22552/ (Markdown: https://insights.sbomify.com/CVE-2020-22552/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-22552
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-22552
- OSV: https://osv.dev/vulnerability/CVE-2020-22552

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-22552/
Summaries are generated and may contain mistakes; the official description above is the record.