# CVE-2021-33539: WEIDMUELLER: WLAN devices affected by authentication bypass vulnerability

> Attackers can bypass web authentication on Weidmüller Industrial WLAN devices by manipulating hostname processing to treat remote traffic as local.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Jun 2021
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-9vqf-5jhj-hm4w

## What is CVE-2021-33539?

CVE-2021-33539 is a high-severity authentication bypass vulnerability in Weidmüller IE-WL(T)-BL-AP-CL-XX, published on 25 Jun 2021. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

In Weidmueller Industrial WLAN devices in multiple versions an exploitable authentication bypass vulnerability exists in the hostname processing. A specially configured device hostname can cause the device to interpret selected remote traffic as local traffic, resulting in a bypass of web authentication. An attacker can send authenticated SNMP requests to trigger this vulnerability.

Weakness: CWE-287 (Improper Authentication)

## Which versions are affected by CVE-2021-33539?

It affects 8 products.


Products: Weidmueller Ie-Wl-Bl-Ap-Cl-Eu Firmware, Weidmueller Ie-Wl-Bl-Ap-Cl-Us Firmware, Weidmueller Ie-Wl-Vl-Ap-Br-Cl-Eu Firmware, Weidmueller Ie-Wl-Vl-Ap-Br-Cl-Us Firmware, Weidmueller Ie-Wlt-Bl-Ap-Cl-Eu Firmware, Weidmueller Ie-Wlt-Bl-Ap-Cl-Us Firmware, Weidmueller Ie-Wlt-Vl-Ap-Br-Cl-Eu Firmware, Weidmueller Ie-Wlt-Vl-Ap-Br-Cl-Us Firmware.

## How do I fix CVE-2021-33539?

No fix has been published for CVE-2021-33539 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-33539 being exploited?

There is no known exploitation of CVE-2021-33539 in the wild and no public exploit code.

## Other vulnerabilities in Weidmüller IE-WL(T)-BL-AP-CL-XX

- [CVE-2021-33528](https://insights.sbomify.com/CVE-2021-33528/): WEIDMUELLER: WLAN devices affected by privilege escalation vulnerability (high 8.8)
- [CVE-2021-33530](https://insights.sbomify.com/CVE-2021-33530/): WEIDMUELLER: WLAN devices affected by OS Command Injection vulnerability (high 8.8)
- [CVE-2021-33531](https://insights.sbomify.com/CVE-2021-33531/): WEIDMUELLER: WLAN devices affected by Hard-coded Credentials vulnerability (high 8.8)
- [CVE-2021-33532](https://insights.sbomify.com/CVE-2021-33532/): WEIDMUELLER: WLAN devices affected by OS Command Injection vulnerability (high 8.8)
- [CVE-2021-33533](https://insights.sbomify.com/CVE-2021-33533/): WEIDMUELLER: WLAN devices affected by OS Command Injection vulnerability (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33539 and fix it if it is affected.

What it is: CVE-2021-33539 is a high-severity authentication bypass vulnerability in Weidmüller IE-WL(T)-BL-AP-CL-XX, published on 25 Jun 2021. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-33539 in the wild and no public exploit code.

Affected product: Weidmüller IE-WL(T)-BL-AP-CL-XX. 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-2021-33539/ (Markdown: https://insights.sbomify.com/CVE-2021-33539/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33539
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33539
- OSV: https://osv.dev/vulnerability/CVE-2021-33539

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33539/
Summaries are generated and may contain mistakes; the official description above is the record.