# CVE-2026-28207: Zen-C Vulnerable to Command Injection via Malicious Output Filename

> Local attackers can execute arbitrary shell commands via crafted output filenames in the Zen C compiler due to unsafe system() usage.

- **Severity:** Medium 6.6 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 26 Feb 2026
- **Updated:** 2 Mar 2026
- **Also known as:** GHSA-9rff-x96h-76h2

## What is CVE-2026-28207?

CVE-2026-28207 is a medium-severity command injection vulnerability in z-libs Zen-C, published on 26 Feb 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Zen C is a systems programming language that compiles to human-readable GNU C/C11. Prior to version 0.4.2, a command injection vulnerability (CWE-78) in the Zen C compiler allows local attackers to execute arbitrary shell commands by providing a specially crafted output filename via the `-o` command-line argument. The vulnerability existed in the `main` application logic (specifically in `src/main.c`), where the compiler constructed a shell command string to invoke the backend C compiler. This command string was built by concatenating various arguments, including the user-controlled output filename, and was subsequently executed using the `system()` function. Because `system()` invokes a shell to parse and execute the command, shell metacharacters within the output filename were interpreted by the shell, leading to arbitrary command execution. An attacker who can influence the command-line arguments passed to the `zc` compiler (like through a build script or a CI/CD pipeline configuration) can execute arbitrary commands with the privileges of the user running the compiler. The vulnerability has been fixed in version 0.4.2 by removing `system()` calls, implementing `ArgList`, and internal argument handling. Users are advised to update to Zen C version v0.4.2 or later.

Weakness: CWE-78 (Improper Neutralization of Special Elements used in an OS Command)

## Which versions are affected by CVE-2026-28207?

It affects 1 product.


Products: Zenc-Lang Zen C.

## How do I fix CVE-2026-28207?

No fix has been published for CVE-2026-28207 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-28207 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28207 exists.

## Other vulnerabilities in z-libs Zen-C

- [CVE-2026-33491](https://insights.sbomify.com/CVE-2026-33491/): Zen-C has Stack-Based Buffer Overflow in Identifier Mangling (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-28207 and fix it if it is affected.

What it is: CVE-2026-28207 is a medium-severity command injection vulnerability in z-libs Zen-C, published on 26 Feb 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-28207 exists.

Affected product: z-libs Zen-C. 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-2026-28207/ (Markdown: https://insights.sbomify.com/CVE-2026-28207/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-28207
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-28207
- OSV: https://osv.dev/vulnerability/CVE-2026-28207

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-28207/
Summaries are generated and may contain mistakes; the official description above is the record.