# CVE-2021-43206: Information disclosure in Fortinet FortiOS, FortiProxy

> Malicious webservers can retrieve client usernames and IP addresses from Fortinet proxy error pages via crafted HTTP requests.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:N/E:P/RL:U/RC:C`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 4 May 2022
- **Updated:** 22 Oct 2024
- **Also known as:** GHSA-9645-9xqx-6r37

## What is CVE-2021-43206?

CVE-2021-43206 is a medium-severity vulnerability in Fortinet Fortios, published on 4 May 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A server-generated error message containing sensitive information in Fortinet FortiOS 7.0.0 through 7.0.3, 6.4.0 through 6.4.8, 6.2.x, 6.0.x and FortiProxy 7.0.0 through 7.0.1, 2.0.x allows malicious webservers to retrieve a web proxy's client username and IP via same origin HTTP requests triggering proxy-generated HTTP status codes pages.

Weakness: CWE-209 (Generation of Error Message Containing Sensitive Information)

## Which versions are affected by CVE-2021-43206?

It affects 2 products.


Products: Fortinet Fortios, Fortinet Fortiproxy.

## How do I fix CVE-2021-43206?

No fix has been published for CVE-2021-43206 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-43206 being exploited?

There is no known exploitation of CVE-2021-43206 in the wild and no public exploit code.

## Other vulnerabilities in Fortinet Fortios

- [CVE-2024-23113](https://insights.sbomify.com/CVE-2024-23113/): Fortinet Multiple Products Format String (critical 9.8, exploited in the wild)
- [CVE-2022-40684](https://insights.sbomify.com/CVE-2022-40684/): Fortinet Multiple Products Authentication Bypass (critical 9.8, exploited in the wild)
- [CVE-2024-55591](https://insights.sbomify.com/CVE-2024-55591/): Fortinet FortiOS and FortiProxy Authentication Bypass (critical 9.6, exploited in the wild)
- [CVE-2024-21762](https://insights.sbomify.com/CVE-2024-21762/): Fortinet FortiOS Out-of-Bound Write (critical 9.6, exploited in the wild)
- [CVE-2022-42475](https://insights.sbomify.com/CVE-2022-42475/): Fortinet FortiOS Heap-Based Buffer Overflow (critical 9.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-43206 and fix it if it is affected.

What it is: CVE-2021-43206 is a medium-severity vulnerability in Fortinet Fortios, published on 4 May 2022. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-43206 in the wild and no public exploit code.

Affected product: Fortinet Fortios. 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-2021-43206/ (Markdown: https://insights.sbomify.com/CVE-2021-43206/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-43206
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-43206
- OSV: https://osv.dev/vulnerability/CVE-2021-43206

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-43206/
Summaries are generated and may contain mistakes; the official description above is the record.