CVE-2026-26067: October: Safe Mode Bypass via CSS Preprocessor Compilers
A server-side information disclosure vulnerability was identified in the handling of CSS preprocessor files. Backend users with Editor permissions could craft .less, .sass, or .scss files that leverage the compiler's import functionality to read arbitrary files from the server. This worked even with cms.safemode enabled.
Impact - Potential exposure of sensitive server-side files - Requires authenticated backend access with Editor permissions - Only relevant when cms.safemode is enabled (otherwise direct PHP injection is already possible)
Patches The vulnerability has been patched in v3.7.14 and v4.1.10. When cms.safemode is enabled, .less, .sass, and .scss files can no longer be created, uploaded, or edited across the CMS editor, media manager, and file upload interfaces. All users are encouraged to upgrade to the latest patched version.
Workarounds If upgrading immediately is not possible: - Set cms.editableassettypes config to ['css', 'js'] to remove preprocessor file types from the editor - Restrict Editor tool access to fully trusted administrators only
- Reported by Chris Alupului
Other sources
October is a Content Management System (CMS) and web platform. Prior to 3.7.14 and 4.1.10, a server-side information disclosure vulnerability was identified in the handling of CSS preprocessor files. Backend users with Editor permissions could craft .less, .sass, or .scss files that leverage the compiler's import functionality to read arbitrary files from the server. This worked even with cms.safemode enabled. This vulnerability is fixed in 3.7.14 and 4.1.10.
— MITRE
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-26067?
CVE-2026-26067 is categorized as a medium-severity vulnerability due to potential information disclosure risks.
How do I fix CVE-2026-26067?
To fix CVE-2026-26067, upgrade your October CMS to version 3.7.14 or 4.1.10 or later.
Who is affected by CVE-2026-26067?
Backend users with Editor permissions in versions prior to 3.7.14 and 4.1.10 of October CMS are affected by CVE-2026-26067.
What type of vulnerability is CVE-2026-26067?
CVE-2026-26067 is a server-side information disclosure vulnerability related to the handling of CSS preprocessor files.
What are the consequences of CVE-2026-26067?
The consequences of CVE-2026-26067 include unauthorized access to sensitive information by users with elevated privileges.