# CVE-2016-2056: Command injection in n/a

> Remote authenticated users can execute arbitrary commands via shell metacharacters in the adduser_name argument of Xymon web components.

- **Severity:** High 8.8 (`CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/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:** Yes
- **Published:** 13 Apr 2016
- **Updated:** 5 Aug 2024
- **Also known as:** DEBIAN-CVE-2016-2056, GHSA-9xfv-r389-8vvf

## What is CVE-2016-2056?

CVE-2016-2056 is a high-severity command injection vulnerability in Debian Debian Linux, published on 13 Apr 2016. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

xymond in Xymon 4.1.x, 4.2.x, and 4.3.x before 4.3.25 allow remote authenticated users to execute arbitrary commands via shell metacharacters in the adduser_name argument in (1) web/useradm.c or (2) web/chpasswd.c.

Weakness: CWE-77 (Improper Neutralization of Special Elements used in a Command)

## Which versions are affected by CVE-2016-2056?

It affects 2 products.


Products: Debian Debian Linux, Xymon Xymon.

## How do I fix CVE-2016-2056?

Upgrade to a fixed version.

## Is CVE-2016-2056 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-2056 exists.

Public exploit code:

- Xymon useradm Command Execution (metasploit)
- Xymon 4.3.25 - useradm Command Execution (Metasploit) (exploitdb)

## Other vulnerabilities in Debian Debian Linux

- [CVE-2015-3306](https://insights.sbomify.com/CVE-2015-3306/): ProFTPD Improper Access Control (critical 10.0, exploited in the wild)
- [CVE-2025-49113](https://insights.sbomify.com/CVE-2025-49113/): RoundCube Webmail Deserialization of Untrusted Data (critical 9.9, exploited in the wild)
- [CVE-2026-24061](https://insights.sbomify.com/CVE-2026-24061/): GNU InetUtils Argument Injection (critical 9.8, exploited in the wild)
- [CVE-2025-39682](https://insights.sbomify.com/CVE-2025-39682/): Linux Kernel Improper Check for Unusual or Exceptional Conditions (critical 9.8, exploited in the wild)
- [CVE-2024-9680](https://insights.sbomify.com/CVE-2024-9680/): Mozilla Firefox Use-After-Free (critical 9.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-2056 and fix it if it is affected.

What it is: CVE-2016-2056 is a high-severity command injection vulnerability in Debian Debian Linux, published on 13 Apr 2016. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2016-2056 exists.

Affected product: Debian Debian Linux. 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-2016-2056/ (Markdown: https://insights.sbomify.com/CVE-2016-2056/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-2056
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-2056
- OSV: https://osv.dev/vulnerability/CVE-2016-2056

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From sbomify Insights: https://insights.sbomify.com/CVE-2016-2056/
Summaries are generated and may contain mistakes; the official description above is the record.