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Medium

October CMS has Safe Mode Bypass via CSS Preprocessor Compilers

  • Disclosed: 21.04.2026
  • Updated: 11.10.2026 10:22

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.safe_mode enabled.

Impact

  • Potential exposure of sensitive server-side files
  • Requires authenticated backend access with Editor permissions
  • Only relevant when cms.safe_mode 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.safe_mode 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.editable_asset_types 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

Affected software

Click a technology to see all vulnerabilities affecting it.

PlatformPackageVulnerable versionsFixed in
Composer package october/system < 3.7.14, >= 4.0.0, < 4.1.10 3.7.14, 4.1.10

References

CVSS score 4.9/10
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Weakness (CWE)
CWE-184, CWE-200, CWE-22
Platform
Composer
Package
october/system
Disclosed
21.04.2026
Updated
11.10.2026 10:22

Sources and licenses

OSV / GitHub Advisory Database - GHSA-3888-q23f-x7qh - CC BY 4.0

Vulnerability history: october/system

All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.

All (25) in the archive
Total entries
25
First → latest
06.2020 09.2026
Without a fix
0
Exploited in attacks
1

Severity breakdown

  • Critical 1
  • High 8
  • Medium 9
  • Low 7

Disclosures per year

Severity:
  1. October CMS has Safe Mode Bypass via CSS Preprocessor Compilers this entry
    Medium · 4.9 CVE-2026-26067 < 3.7.14, >= 4.0.0, < 4.1.10 3.7.14, 4.1.10
  2. October CMS safe mode bypass using Twig sandbox escape
    Critical · 9.1 CVE-2023-44382 >= 3.0.0, < 3.4.15 3.4.15
  3. October CMS Safe Mode bypass leads to authenticated Remote Code Execution
    High · 7.2 CVE-2022-35944 >= 2.0.0, < 2.2.34, >= 3.0.0, < 3.0.66 2.2.34, 3.0.66
  4. October CMS upload process vulnerable to RCE via Race Condition
    High · 8.1 CVE-2022-24800 < 1.0.476, >= 1.1.0, < 1.1.12, >= 2.0.0, < 2.2.15 1.0.476, 1.1.12, 2.2.15
  5. Authenticated remote code execution in October CMS
    High · 7.2 CVE-2022-21705 < 1.0.474, >= 1.1.0, < 1.1.10, >= 2.0.0, < 2.1.27 1.0.474, 1.1.10, 2.1.27
  6. october/system arbitrary code execution
    High · 8.8 CVE-2021-32650 >= 1.1.0, < 1.1.6, < 1.0.473 1.1.6, 1.0.473
  7. October/System authenticated file write leads to remote code execution
    High · 8.8 CVE-2021-32649 >= 1.1.0, < 1.1.6, < 1.0.473 1.1.6, 1.0.473
  8. Deleted Admin Can Sign In to Admin Interface
    High · 7.2 CVE-2021-41126 >= 2.1.0, < 2.1.12 2.1.12
  9. October CMS auth bypass and account takeover
    High · 7.4 CVE-2021-29487 < 1.0.472, >= 1.1.1, < 1.1.5 1.0.472, 1.1.5
  10. Account Takeover in Octobercms
    High · 8.2 Exploited in attacks CVE-2021-32648 < 1.0.472, >= 1.1.1, < 1.1.5 1.0.472, 1.1.5

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