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

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-54256
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-26 18:16:40 UTC
Updated2026-08-27 17:18:47 UTC
DescriptionWinter CMS is a content management system built on the Laravel PHP framework. In versions up to and including 1.2.12, the backend FileUpload form widget trusted an attacker-controlled file_id POST parameter when resolving the attachment it operates on, allowing an authenticated backend user to read and modify attachment records belonging to other users or records. The widget's getFileRecord() lookup resolved the posted id against the global system_files table without verifying that the file belonged to the widget's own relation, parent record, or deferred-binding session. Because all attachments share a single File model and table and attachment ids are sequential integers that are easily enumerated, a user reaching any form with a fileupload field, including the built-in My Account avatar field that requires no specific permission, could target arbitrary attachments to modify their title and description via onSaveAttachmentConfig and change their sort order via onSortAttachments, which passed posted ids straight to an unscoped update. CSRF tokens remain enforced, so exploitation requires a valid authenticated backend session with any level of access. This issue is fixed in version 1.2.13.

Risk And Classification

Primary CVSS: v3.1 5.4 MEDIUM from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

EPSS: 0.001430000 probability, percentile 0.039400000 (date 2026-08-27)

Problem Types: CWE-284 | CWE-639 | CWE-284 CWE-284: Improper Access Control | CWE-639 CWE-639: Authorization Bypass Through User-Controlled Key

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N
3.1CNADECLARED5.4MEDIUMCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Wintercms Winter affected < 1.2.13 Not specified

References

ReferenceSourceLinkTags
github.com/wintercms/winter/security/advisories/GHSA-3277-h8g9-qj5f [email protected] github.com
github.com/wintercms/winter/commit/9cb0ae5f9d837db141ab111c6a7de8eed9603d25 [email protected] github.com
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