# CVE-2021-30120: 2FA bypass in Kaseya VSA <= v9.5.6

> Attackers can bypass two-factor authentication by intercepting and modifying client-side responses, allowing unauthorized access to Kaseya VSA accounts.

- **Severity:** Critical 9.9 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/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:** 9 Jul 2021
- **Updated:** 14 Aug 2026
- **Also known as:** GHSA-r6j9-rwx4-qcj3

## What is CVE-2021-30120?

CVE-2021-30120 is a critical authentication bypass vulnerability in n/a, published on 9 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Kaseya VSA before 9.5.7 allows attackers to bypass the 2FA requirement. The need to use 2FA for authentication in enforce client-side instead of server-side and can be bypassed using a local proxy. Thus rendering 2FA useless. Detailed description --- During the login process, after the user authenticates with username and password, the server sends a response to the client with the booleans MFARequired and MFAEnroled. If the attacker has obtained a password of a user and used an intercepting proxy (e.g. Burp Suite) to change the value of MFARequered from True to False, there is no prompt for the second factor, but the user is still logged in.

Weakness: CWE-669 (Incorrect Resource Transfer Between Spheres)

## Which versions are affected by CVE-2021-30120?

It affects 1 product.


Products: Kaseya Vsa.

## How do I fix CVE-2021-30120?

No fix has been published for CVE-2021-30120 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-30120 being exploited?

There is no known exploitation of CVE-2021-30120 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2021-30117](https://insights.sbomify.com/CVE-2021-30117/): Authenticated SQL injection in Kaseya VSA < v9.5.6 (critical 9.8)
- [CVE-2021-30118](https://insights.sbomify.com/CVE-2021-30118/): Unauthenticated Remote Code Execution in Kaseya VSA < v9.5.5 (critical 9.8)
- [CVE-2021-30201](https://insights.sbomify.com/CVE-2021-30201/): Unauthenticated XML External Entity vulnerability in Kaseya VSA < v9.5.6 (high 7.5)
- [CVE-2019-14510](https://insights.sbomify.com/CVE-2019-14510/): Hardcoded credentials in n/a (medium 6.7)
- [CVE-2021-30121](https://insights.sbomify.com/CVE-2021-30121/): (Semi-)Authenticated local file inclusion in Kaseya VSA < v9.5.6 (medium 6.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-30120 and fix it if it is affected.

What it is: CVE-2021-30120 is a critical authentication bypass vulnerability in n/a, published on 9 Jul 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-2021-30120 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-2021-30120/ (Markdown: https://insights.sbomify.com/CVE-2021-30120/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-30120
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-30120
- OSV: https://osv.dev/vulnerability/CVE-2021-30120

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-30120/
Summaries are generated and may contain mistakes; the official description above is the record.