CVE-2026-63179

Received Received - Intake

Authenticated File Disclosure in Winter CMS via LESS Import Injection

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: GitHub, Inc.

Description

Winter CMS is a content management system built on the Laravel PHP framework. In versions up to and including 1.2.12, authenticated backend users can disclose arbitrary files readable by the PHP process by injecting @import (inline) directives into LESS source that the backend compiles, because the LESS parser was instantiated without a safe import resolver and fell back to the raw attacker-supplied path when no allowed root matched. The flaw is reachable through four entry points that share the same root cause: the Brand Settings custom_css field, the Editor Settings html_custom_styles field, the Mail Brand Settings colour-picker fields whose values are concatenated into LESS source without escaping, and theme .less, .sass, and .scss assets compiled when served. Both absolute paths and .. traversal outside the asset's own tree were accepted, so an attacker could read any file the web process can access, most significantly the application .env file and the APP_KEY and database credentials it contains. Exploitation requires a backend account holding one of the associated permissions, which are assigned by default to the built-in Developer role. This issue is fixed in version 1.2.13.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-26

Last Modified

2026-08-26

Generated

2026-08-27

AI Q&A

2026-08-27

EPSS Evaluated

N/A

NVD

CVE-2026-63179

Affected Vendors & Products

Vendor	Product	Version / Range
winter_cms	winter_cms	to 1.2.12 (inc)
winter_cms	winter_cms	1.2.13

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-22	The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.

Attack-Flow Graph

Executive Summary

This vulnerability affects Winter CMS versions up to 1.2.12. Authenticated backend users can exploit it by injecting @import directives into LESS source code. The LESS parser lacks a safe import resolver, allowing attackers to read arbitrary files accessible by the PHP process. This includes sensitive files like the application .env file containing APP_KEY and database credentials.

Detection Guidance

This vulnerability requires authenticated backend access to exploit. To detect it, check for unauthorized file reads or suspicious LESS/Sass compilation requests in logs. Look for entries involving @import directives with absolute paths or path traversal (e.g., ../) in custom_css, html_custom_styles, or theme asset files. Review file access logs for unexpected reads of sensitive files like .env.

Impact Analysis

An attacker with a backend account (default Developer role) could access sensitive files like the .env file, exposing APP_KEY, database credentials, and other confidential data. This could lead to further compromise of the application or server.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, violating GDPR (data protection) and HIPAA (health information privacy) requirements. Exposure of credentials or personal data may result in non-compliance and potential legal consequences.

Mitigation Strategies

Upgrade Winter CMS to version 1.2.13 or later to address the vulnerability. Remove or restrict backend user permissions, especially for the Developer role, to limit access to sensitive fields.

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