Описание
AlchemyCMS: Authenticated Remote Code Execution (RCE) via eval injection in ResourcesHelper
Summary
A vulnerability was discovered during a manual security audit of the AlchemyCMS source code. The application uses the Ruby eval() function to dynamically execute a string provided by the resource_handler.engine_name attribute in Alchemy::ResourcesHelper#resource_url_proxy.
Details
The vulnerability exists in app/helpers/alchemy/resources_helper.rb at line 28. The code explicitly bypasses security linting with # rubocop:disable Security/Eval, indicating that the use of a dangerous function was known but not properly mitigated.
Since engine_name is sourced from module definitions that can be influenced by administrative configurations, it allows an authenticated attacker to escape the Ruby sandbox and execute arbitrary system commands on the host OS.
But, for this attack to be possible local file access to the alchemy project or the source on a remote server is necessary in order to manipulate the module config file, though.
PoC (Proof of Concept)
The following standalone Ruby script demonstrates that the eval sink is directly exploitable:
Ссылки
- https://github.com/AlchemyCMS/alchemy_cms/security/advisories/GHSA-2762-657x-v979
- https://nvd.nist.gov/vuln/detail/CVE-2026-23885
- https://github.com/AlchemyCMS/alchemy_cms/commit/55d03ec600fd9e07faae1138b923790028917d26
- https://github.com/AlchemyCMS/alchemy_cms/commit/563c4ce45bf5813b7823bf3403ca1fc32cb769e7
- https://github.com/AlchemyCMS/alchemy_cms/releases/tag/v7.4.12
- https://github.com/AlchemyCMS/alchemy_cms/releases/tag/v8.0.3
- https://github.com/rubysec/ruby-advisory-db/blob/master/gems/alchemy_cms/CVE-2026-23885.yml
Пакеты
alchemy_cms
< 7.4.12
7.4.12
alchemy_cms
>= 8.0.0.a, < 8.0.3
8.0.3
Связанные уязвимости
Alchemy is an open source content management system engine written in Ruby on Rails. Prior to versions 7.4.12 and 8.0.3, the application uses the Ruby `eval()` function to dynamically execute a string provided by the `resource_handler.engine_name` attribute in `Alchemy::ResourcesHelper#resource_url_proxy`. The vulnerability exists in `app/helpers/alchemy/resources_helper.rb` at line 28. The code explicitly bypasses security linting with `# rubocop:disable Security/Eval`, indicating that the use of a dangerous function was known but not properly mitigated. Since `engine_name` is sourced from module definitions that can be influenced by administrative configurations, it allows an authenticated attacker to escape the Ruby sandbox and execute arbitrary system commands on the host OS. Versions 7.4.12 and 8.0.3 fix the issue by replacing `eval()` with `send()`.