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CVE-2026-26067

October: Safe Mode Bypass via CSS Preprocessor Compilers

4.9 MediumFix available

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.safe_mode enabled. This vulnerability is fixed in 3.7.14 and 4.1.10.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
High
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.25%Up 0.2 points since Apr 22, 2026
90%50%10%1%

What each source reports

CVE List Score used 4.9

October: Safe Mode Bypass via CSS Preprocessor Compilers

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.safe_mode enabled. This vulnerability is fixed in 3.7.14 and 4.1.10.

Record
CVE-2026-26067
CVSS 3.1
4.9 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-863, CWE-184
Updated
2026-11-02
EUVDEUVD-2026-24153 4.9

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.safe_mode enabled. This vulnerability is fixed in 3.7.14 and 4.1.10.

Record
EUVD-2026-24153
CVSS 3.1
4.9 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-3888-q23f-x7qh 4.9

October CMS has 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.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

Record
GHSA-3888-q23f-x7qh
CVSS 3.1
4.9 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-22, CWE-184, CWE-200
Updated
2026-11-02
NVD 4.9

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.safe_mode enabled. This vulnerability is fixed in 3.7.14 and 4.1.10.

Record
CVE-2026-26067
CVSS 3.1
4.9 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-184, CWE-863
Updated
2026-11-02
OSVGHSA-3888-q23f-x7qh 4.9

October CMS has 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.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

Record
GHSA-3888-q23f-x7qh
CVSS 3.1
4.9 MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-184, CWE-200, CWE-22
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
october/system
Packagist
 before 3.7.14
3.7.14
october/system
Packagist
 4.0.0 up to 4.1.10
4.1.10
october/system
Packagist
 before 3.7.14, plus listed versions
v1.0.319v1.0.320v1.0.321v1.0.322v1.0.323
Show 45 moreShow less
v1.0.324v1.0.325v1.0.326v1.0.327v1.0.328v1.0.329v1.0.330v1.0.331v1.0.332v1.0.333v1.0.334v1.0.335v1.0.336v1.0.337v1.0.338v1.0.339v1.0.340v1.0.341v1.0.342v1.0.343v1.0.344v1.0.345v1.0.346v1.0.347v1.0.348v1.0.349v1.0.350v1.0.351v1.0.352v1.0.353v1.0.354v1.0.355v1.0.356v1.0.357v1.0.358v1.0.359v1.0.360v1.0.361v1.0.362v1.0.363v1.0.364v1.0.365v1.0.366v1.0.367v1.0.368
3.7.14

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-26067 is a medium vulnerability (CVSS 4.9) in Octobercms October, published April 21, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.25%, the 15th percentile. Fixed in october/system 3.7.14.

References

This page doesn't list everything

Left out here: 119 versions. The JSON record has them.

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