CVE-2026-26067: October/system October CMS Has Safe Mode Vulnerability

MODERATE
Advisory Identifier: GHSA-3888-q23f-x7qh
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CVSS 4.9
CWE-200 CWE-184 CWE-22
Published
Advisory Summary

CVE-2026-26067 is a MODERATE (CVSS 4.9) october cms has safe mode vulnerability (CWE-200: Exposure of Sensitive Information to an Unauthorized Actor) affecting October/system libraries in the Packagist ecosystem. The issue involves october cms has safe mode bypass via css preprocessor compilers. Remediation is available by upgrading affected packages to version 3.7.14, 4.1.10.

CVE-2026-26067 at a Glance

CVE Identifier CVE-2026-26067
GHSA Identifier GHSA-3888-q23f-x7qh
Severity MODERATE
CVSS v3.1 Base Score 4.9
CWE Classification CWE-200: Exposure of Sensitive Information to an Unauthorized Actor
Affected Product October/system
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 4.9

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required High (PR:H)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality High (C:H)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2026-26067

To remediate this vulnerability, upgrade all affected October/system dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

october/system fixed: 3.7.14 
Upgrade october/system to 3.7.14
october/system fixed: 4.1.10 
Upgrade october/system to 4.1.10
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for october/system

How to Check if You Are Affected

To determine whether your application is affected by CVE-2026-26067, inspect your project dependencies for October/system:

inspect dependencies for october/system

Analyze the terminal output to locate any version of October/system in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 3.7.14), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor, where the product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. In October/system, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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](https://github.com/neosprings)

CVE-2026-26067 Affected October/system Versions

2 component(s)
Fixed Versions:
3.7.144.1.10
Product / Package Ecosystem Affected Versions Fixed Version
october/system
 Packagist
< 3.7.14
3.7.14
october/system
 Packagist
≥ 4.0.0
< 4.1.10
4.1.10

References

GitHub Advisory / Wiki ADVISORY
https://github.com/octobercms/october/security/advisories/GHSA-3888-q23f-x7qh
NVD — CVE-2026-26067 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-26067
October/system Source Repository REPOSITORY
https://github.com/octobercms/october

Frequently Asked Questions

What is CVE-2026-26067?
CVE-2026-26067 is a security vulnerability in October/system involving October CMS has Safe Mode Bypass via CSS Preprocessor Compilers under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor.
Which October/system versions are affected?
Affected versions include releases prior to 3.7.14, 4.1.10 across affected packages: october/system.
What version fixes CVE-2026-26067?
Upgrading to 3.7.14, 4.1.10 (or the latest patched release for your respective branch) resolves the vulnerability.
Is october/system affected?
Yes, october/system is affected in releases prior to 3.7.14, 4.1.10. Upgrade your dependency to 3.7.14, 4.1.10 or later.
What is the CVSS score of CVE-2026-26067?
CVE-2026-26067 has a CVSS v3.1 base score of 4.9 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N.
What CWE is associated with CVE-2026-26067?
CVE-2026-26067 is classified under CWE-200: Exposure of Sensitive Information to an Unauthorized Actor (The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.).
How can I check Packagist dependencies for CVE-2026-26067?
Run the dependency tree command: 'inspect dependencies for october/system'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-3888-q23f-x7qh",
  "modified" : "2026-04-24T21:06:45Z",
  "published" : "2026-04-21T16:43:49Z",
  "aliases" : [ "CVE-2026-26067" ],
  "summary" : "October CMS has Safe Mode Bypass via CSS Preprocessor Compilers",
  "details" : "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.\n\n### Impact\n- Potential exposure of sensitive server-side files\n- Requires authenticated backend access with Editor permissions\n- Only relevant when `cms.safe_mode` is enabled (otherwise direct PHP injection is already possible)\n\n### Patches\nThe 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.\n\n### Workarounds\nIf upgrading immediately is not possible:\n- Set `cms.editable_asset_types` config to `['css', 'js']` to remove preprocessor file types from the editor\n- Restrict Editor tool access to fully trusted administrators only\n\n- Reported by [Chris Alupului](https://github.com/neosprings)",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "october/system"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.7.14"
      } ]
    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "october/system"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.1.10"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/octobercms/october/security/advisories/GHSA-3888-q23f-x7qh"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-26067"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/octobercms/october"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-184", "CWE-200", "CWE-22" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-21T16:43:49Z",
    "nvd_published_at" : "2026-04-21T17:16:24Z"
  }
}