# CVE-2021-33903: Auth bypass in n/a

> Attackers can retain SNMPv3 root access after CLI password changes, bypassing authentication updates on LANCOM devices.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 7 Oct 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-h7w5-g7jm-642w

## What is CVE-2021-33903?

CVE-2021-33903 is a high-severity authentication bypass vulnerability in n/a, published on 7 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

In LCOS 10.40 to 10.42.0473-RU3 with SNMPv3 enabled on LANCOM devices, changing the password of the root user via the CLI does not change the password of the root user for SNMPv3 access. (However, changing the password of the root user via LANconfig does change the password of the root user for SNMPv3 access.)

## Which versions are affected by CVE-2021-33903?

It affects 1 product.


Products: Lancom-Systems Lcos.

## How do I fix CVE-2021-33903?

No fix has been published for CVE-2021-33903 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-33903 being exploited?

There is no known exploitation of CVE-2021-33903 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2020-23055](https://insights.sbomify.com/CVE-2020-23055/): Cross-site scripting in n/a (medium 5.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-33903 and fix it if it is affected.

What it is: CVE-2021-33903 is a high-severity authentication bypass vulnerability in n/a, published on 7 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-33903 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-2021-33903/ (Markdown: https://insights.sbomify.com/CVE-2021-33903/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-33903
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-33903
- OSV: https://osv.dev/vulnerability/CVE-2021-33903

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-33903/
Summaries are generated and may contain mistakes; the official description above is the record.