# CVE-2021-33541: Phoenix Contact: ILC1x Industrial controllers affected by Denial-of-Service vulnerability

> Remote attackers can cause a denial of service on Phoenix Contact ILC1x controllers by sending crafted packets, requiring a device restart to restore network connectivity.

- **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:** 25 Jun 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-jwj9-vx74-vv26

## What is CVE-2021-33541?

CVE-2021-33541 is a high-severity denial of service vulnerability in Phoenix Contact ILC1x, published on 25 Jun 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Phoenix Contact Classic Line Controllers ILC1x0 and ILC1x1 in all versions/variants are affected by a Denial-of-Service vulnerability. The communication protocols and device access do not feature authentication measures. Remote attackers can use specially crafted IP packets to cause a denial of service on the PLC's network communication module. A successful attack stops all network communication. To restore the network connectivity the device needs to be restarted. The automation task is not affected.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2021-33541?

It affects 2 products.


Products: Phoenixcontact Ilc1x0 Firmware, Phoenixcontact Ilc1x1 Firmware.

## How do I fix CVE-2021-33541?

No fix has been published for CVE-2021-33541 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-33541 being exploited?

There is no known exploitation of CVE-2021-33541 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33541 and fix it if it is affected.

What it is: CVE-2021-33541 is a high-severity denial of service vulnerability in Phoenix Contact ILC1x, published on 25 Jun 2021. 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-2021-33541 in the wild and no public exploit code.

Affected product: Phoenix Contact ILC1x. 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-2021-33541/ (Markdown: https://insights.sbomify.com/CVE-2021-33541/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33541
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33541
- OSV: https://osv.dev/vulnerability/CVE-2021-33541

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33541/
Summaries are generated and may contain mistakes; the official description above is the record.