# CVE-2026-30940: baserCMS: Path Traversal in Theme File API Leads to Arbitrary File Write and RCE

> An authenticated administrator can exploit path traversal in the theme file API to write arbitrary files, potentially leading to remote code execution.

- **Severity:** High 7.2 (`CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 31 Mar 2026
- **Updated:** 2 Apr 2026
- **Also known as:** GHSA-c5c6-37vq-pjcq

## What is CVE-2026-30940?

CVE-2026-30940 is a high-severity path traversal vulnerability in Basercms Basercms, published on 31 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.

### Official description

baserCMS is a website development framework. Prior to version 5.2.3, a path traversal vulnerability exists in the theme file management API (/baser/api/admin/bc-theme-file/theme_files/add.json) that allows arbitrary file write. An authenticated administrator can include ../ sequences in the path parameter to create a PHP file in an arbitrary directory outside the theme directory, which may result in remote code execution (RCE). This issue has been patched in version 5.2.3.

Weakness: CWE-73 (External Control of File Name or Path), CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-30940?

2 open source packages ship an affected version, including baserproject/basercms. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `baserproject/basercms` | Packagist | All versions | 5.2.3 |
| `baserproject/basercms` | Packagist | All versions | 5.2.3 |

Products: Basercms Basercms.

## How do I fix CVE-2026-30940?

Upgrade baserproject/basercms to 5.2.3 or later.

## Is CVE-2026-30940 being exploited?

There is no known exploitation of CVE-2026-30940 in the wild and no public exploit code.

## Other vulnerabilities in Basercms Basercms

- [CVE-2023-25654](https://insights.sbomify.com/CVE-2023-25654/): baserCMS File Uploader Remote Code Execution (RCE) vulnerability (critical 9.8)
- [CVE-2023-25655](https://insights.sbomify.com/CVE-2023-25655/): baserCMS allows any file to be uploaded (critical 9.8)
- [CVE-2017-10842](https://insights.sbomify.com/CVE-2017-10842/): baserCMS SQL Injection vulnerability (critical 9.8)
- [CVE-2026-30880](https://insights.sbomify.com/CVE-2026-30880/): baserCMS: OS command injection vulnerability in installer (critical 9.2)
- [CVE-2026-21861](https://insights.sbomify.com/CVE-2026-21861/): baserCMS: OS Command Injection Leading to Remote Code Execution (RCE) (critical 9.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-30940 and fix it if it is affected.

What it is: CVE-2026-30940 is a high-severity path traversal vulnerability in Basercms Basercms, published on 31 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-30940 in the wild and no public exploit code.

Affected packages and fixed versions:
- baserproject/basercms (Packagist): affected all versions; fixed in 5.2.3
- baserproject/basercms (Packagist): affected all versions; fixed in 5.2.3

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-2026-30940/ (Markdown: https://insights.sbomify.com/CVE-2026-30940/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-30940
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-30940
- OSV: https://osv.dev/vulnerability/CVE-2026-30940

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-30940/
Summaries are generated and may contain mistakes; the official description above is the record.