# CVE-2021-36166: Auth bypass in Fortinet FortiMail

> Remote attackers can guess administrative authentication tokens by observing system properties, leading to unauthorized access to FortiMail.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:P/RL:U/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 1 Mar 2022
- **Updated:** 25 Oct 2024
- **Also known as:** GHSA-6gm4-rphq-fcfx

## What is CVE-2021-36166?

CVE-2021-36166 is a critical authentication bypass vulnerability in Fortinet FortiMail, published on 1 Mar 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An improper authentication vulnerability in FortiMail before 7.0.1 may allow a remote attacker to efficiently guess one administrative account's authentication token by means of the observation of certain system's properties.

Weakness: CWE-330 (Use of Insufficiently Random Values)

## Which versions are affected by CVE-2021-36166?

It affects 1 product.


Products: Fortinet Fortimail.

## How do I fix CVE-2021-36166?

No fix has been published for CVE-2021-36166 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-36166 being exploited?

There is no known exploitation of CVE-2021-36166 in the wild and no public exploit code.

## Other vulnerabilities in Fortinet FortiMail

- [CVE-2026-104286](https://insights.sbomify.com/CVE-2026-104286/): Fortinet FortiMail Path Traversal (critical 9.8, exploited in the wild)
- [CVE-2021-24007](https://insights.sbomify.com/CVE-2021-24007/): SQL injection in Fortinet FortiMail (critical 9.8)
- [CVE-2020-9294](https://insights.sbomify.com/CVE-2020-9294/): Auth bypass in FortiMail (critical 9.8)
- [CVE-2023-47539](https://insights.sbomify.com/CVE-2023-47539/): Auth bypass in FortiMail (critical 9.0)
- [CVE-2021-24013](https://insights.sbomify.com/CVE-2021-24013/): Path traversal in Fortinet FortiMail (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-36166 and fix it if it is affected.

What it is: CVE-2021-36166 is a critical authentication bypass vulnerability in Fortinet FortiMail, published on 1 Mar 2022. 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-2021-36166 in the wild and no public exploit code.

Affected product: Fortinet FortiMail. 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-2021-36166/ (Markdown: https://insights.sbomify.com/CVE-2021-36166/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-36166
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-36166
- OSV: https://osv.dev/vulnerability/CVE-2021-36166

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-36166/
Summaries are generated and may contain mistakes; the official description above is the record.