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Medium, CVSS 5.4amended

Winter: Authenticated IDOR in backend FileUpload widget allows cross-user access to attachment metadata

CVE-2026-54256GHSA-3277-h8g9-qj5f

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
5.4 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
EPSS
  • CVE-2026-54256: 0.24% estimated exploitation activity in the next 30 days; percentile 15.09 (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 The backend FileUpload form widget trusted an attacker-controlled fileid POST parameter when resolving the attachment it operates on. The lookup (FileUpload::getFileRecord()) resolved the posted id against the global systemfiles table without verifying that the file belonged to the widget's own relation, parent record, or deferred-binding session. Any authenticated backend user who can reach a form containing a fileupload field — including the built-in My Account avatar field, which requires no specific backend permission — could therefore target a System\Models\File record belonging to another user or record and: - modify its title and description via onSaveAttachmentConfig, and - change its sortorder via onSortAttachments (which passed posted ids straight to setSortableOrder(), an unscoped UPDATE ... WHERE id = ?). The same unscoped lookup is reached by onLoadAttachmentConfig, onSaveAttachmentConfig, and onRemoveAttachment. Because all attachments share the single…

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

    Amended from ghsa record GHSA-3277-h8g9-qj5f

  2. Revision 1 · created ·

    Published from osv record GHSA-3277-h8g9-qj5f

Agent brief

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# Patch Next advisory brief: CVE-2026-54256

Advisory: Winter: Authenticated IDOR in backend FileUpload widget allows cross-user access to attachment metadata
IDs: CVE-2026-54256, GHSA-3277-h8g9-qj5f
Record: https://patchnext.com/advisories/cve-2026-54256 (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 5.4)
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-3277-h8g9-qj5f (OSV record GHSA-3277-h8g9-qj5f lists affected ranges: Packagist winter/wn-backend-module >=0 <1.2.13 (fixed))
- Verified: https://github.com/advisories/GHSA-3277-h8g9-qj5f (GitHub-reviewed advisory GHSA-3277-h8g9-qj5f lists affected ranges: Packagist winter/wn-backend-module >=0 <=1.2.12)

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