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Medium, CVSS 4.9amended

Winter: Local File Inclusion through @import directives in LESS compilation of backend customizable stylesheets and theme assets

CVE-2026-63179GHSA-58fp-mcx6-7qf9

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (winter/wn-backend-module 1.2.13), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
4.9 · CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:N/A:N
EPSS
  • CVE-2026-63179: 0.52% estimated exploitation activity in the next 30 days; percentile 43.92 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Impact Affected versions of Winter CMS allow authenticated backend users with the following permissions to disclose arbitrary files readable by the PHP process by injecting @import (inline) "<path" directives into LESS source that the backend compiles. Four entry points share the same root cause: - Brand Settings BrandSetting.customcss field (backend.managebranding) — compiled inline into every backend page's <style block. - Editor Settings EditorSetting.htmlcustomstyles field (backend.manageeditor) — compiled inline into every backend page's <style block. - Mail Brand Settings MailBrandSetting colour-picker fields (system.managemailtemplates) — values are concatenated into LESS source via LessParser::ModifyVars() with no escaping, so any value the form validator does not reject can carry an @import directive. - Theme .less/.sass/.scss assets (cms.manageassets) — compiled through System\Classes\CombineAssets when served, with the same LessParser configuration. Both absolute paths and…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-58fp-mcx6-7qf9

  2. Revision 1 · created ·

    Published from osv record GHSA-58fp-mcx6-7qf9

Agent brief

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# Patch Next advisory brief: CVE-2026-63179

Advisory: Winter: Local File Inclusion through @import directives in LESS compilation of backend customizable stylesheets and theme assets
IDs: CVE-2026-63179, GHSA-58fp-mcx6-7qf9
Record: https://patchnext.com/advisories/cve-2026-63179 (revision 2, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: winter/wn-backend-module 1.2.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist winter/wn-backend-module: affected <= 1.2.12; fixed in 1.2.13

## Suggested inspection (read-only)
- Packagist winter/wn-backend-module: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on winter/wn-backend-module.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-58fp-mcx6-7qf9 (OSV record GHSA-58fp-mcx6-7qf9 lists affected ranges: Packagist winter/wn-backend-module >=0 <1.2.13 (fixed))
- Verified: https://github.com/advisories/GHSA-58fp-mcx6-7qf9 (GitHub-reviewed advisory GHSA-58fp-mcx6-7qf9 lists affected ranges: Packagist winter/wn-backend-module >=0 <=1.2.12)

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