# CVE-2021-42073: Auth bypass in n/a

> Attackers can bypass authentication in Barrier by guessing client labels, allowing them to capture input events and modify clipboard content on the server.

- **Severity:** High 8.2 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 8 Nov 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-fm32-wgpg-7rc9

## What is CVE-2021-42073?

CVE-2021-42073 is a high-severity authentication bypass vulnerability in n/a, published on 8 Nov 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An issue was discovered in Barrier before 2.4.0. An attacker can enter an active session state with the barriers component (aka the server-side implementation of Barrier) simply by supplying a client label that identifies a valid client configuration. This label is "Unnamed" by default but could instead be guessed from hostnames or other publicly available information. In the active session state, an attacker can capture input device events from the server, and also modify the clipboard content on the server.

Weakness: CWE-384 (Session Fixation)

## Which versions are affected by CVE-2021-42073?

It affects 1 product.


Products: Barrier Project Barrier.

## How do I fix CVE-2021-42073?

Upgrade to a fixed version.

## Is CVE-2021-42073 being exploited?

There is no known exploitation of CVE-2021-42073 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-42072](https://insights.sbomify.com/CVE-2021-42072/): Auth bypass in n/a (high 8.8)
- [CVE-2021-42074](https://insights.sbomify.com/CVE-2021-42074/): Use after free in n/a (high 7.5)
- [CVE-2021-42075](https://insights.sbomify.com/CVE-2021-42075/): Denial of service in n/a (high 7.5)
- [CVE-2021-42076](https://insights.sbomify.com/CVE-2021-42076/): Denial of service in n/a (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-42073 and fix it if it is affected.

What it is: CVE-2021-42073 is a high-severity authentication bypass vulnerability in n/a, published on 8 Nov 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-2021-42073 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-2021-42073/ (Markdown: https://insights.sbomify.com/CVE-2021-42073/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-42073
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-42073
- OSV: https://osv.dev/vulnerability/CVE-2021-42073

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-42073/
Summaries are generated and may contain mistakes; the official description above is the record.