# CVE-2021-32747: Custom variable protection and blacklists can be circumvented

> Attackers can bypass custom variable protection rules in Icinga Web 2 by using an undocumented URL parameter, exposing sensitive configuration secrets.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 12 Jul 2021
- **Updated:** 3 Aug 2024
- **Also known as:** DEBIAN-CVE-2021-32747, GHSA-2xv9-886q-p7xx, UBUNTU-CVE-2021-32747

## What is CVE-2021-32747?

CVE-2021-32747 is a medium-severity vulnerability in icingaweb2, published on 12 Jul 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Icinga Web 2 is an open source monitoring web interface, framework, and command-line interface. A vulnerability in which custom variables are exposed to unauthorized users exists between versions 2.0.0 and 2.8.2. Custom variables are user-defined keys and values on configuration objects in Icinga 2. These are commonly used to reference secrets in other configurations such as check commands to be able to authenticate with a service being checked. Icinga Web 2 displays these custom variables to logged in users with access to said hosts or services. In order to protect the secrets from being visible to anyone, it's possible to setup protection rules and blacklists in a user's role. Protection rules result in `***` being shown instead of the original value, the key will remain. Backlists will hide a custom variable entirely from the user. Besides using the UI, custom variables can also be accessed differently by using an undocumented URL parameter. By adding a parameter to the affected routes, Icinga Web 2 will show these columns additionally in the respective list. This parameter is also respected when exporting to JSON or CSV. Protection rules and blacklists however have no effect in this case. Custom variables are shown as-is in the result. The issue has been fixed in the 2.9.0, 2.8.3, and 2.7.5 releases. As a workaround, one may set up a restriction to hide hosts and services with the custom variable in question.

Weakness: CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2021-32747?

It affects 1 product.


Products: Icinga Icinga.

## How do I fix CVE-2021-32747?

Upgrade to a fixed version.

## Is CVE-2021-32747 being exploited?

There is no known exploitation of CVE-2021-32747 in the wild and no public exploit code.

## Other vulnerabilities in icingaweb2

- [CVE-2025-48057](https://insights.sbomify.com/CVE-2025-48057/): Icinga 2 certificate renewal might incorrectly renew an invalid certificate (critical 9.3)
- [CVE-2020-29663](https://insights.sbomify.com/CVE-2020-29663/): Security feature bypass in n/a (critical 9.1)
- [CVE-2024-24820](https://insights.sbomify.com/CVE-2024-24820/): Icinga Director configuration is susceptible to Cross-Site Request Forgery (high 8.3)
- [CVE-2018-6535](https://insights.sbomify.com/CVE-2018-6535/): Information disclosure in n/a (high 8.1)
- [CVE-2020-14004](https://insights.sbomify.com/CVE-2020-14004/): Path traversal in n/a (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-32747 and fix it if it is affected.

What it is: CVE-2021-32747 is a medium-severity vulnerability in icingaweb2, published on 12 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-2021-32747 in the wild and no public exploit code.

Affected product: icingaweb2. 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-2021-32747/ (Markdown: https://insights.sbomify.com/CVE-2021-32747/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-32747
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-32747
- OSV: https://osv.dev/vulnerability/CVE-2021-32747

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-32747/
Summaries are generated and may contain mistakes; the official description above is the record.