CVE-2026-63179 Winter: Local File Inclusion through @import directives in LESS compilation of backend customizable stylesheets and theme assets
Authenticated backend users can read arbitrary files, including sensitive configuration, via path traversal in LESS compilation.
- Exploited in the wild
- Not known
- Login needed
- An administrator
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-63179?
CVE-2026-63179 is a medium-severity path traversal vulnerability in wintercms winter, published on 26 Aug 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Official 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.
Weakness: CWE-22
Which versions are affected by CVE-2026-63179?
2 open source packages ship an affected version, including winter/wn-backend-module.
| Package | Affected | Fixed in |
|---|---|---|
winter/wn-backend-module Packagist | All versions | 1.2.13 |
winter/wn-backend-module Packagist | All versions | 1.2.13 |
How do I fix CVE-2026-63179?
Upgrade winter/wn-backend-module to 1.2.13 or later.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-63179 being exploited?
There is no known exploitation of CVE-2026-63179 in the wild and no public exploit code.
Sources
Also known as GHSA-58fp-mcx6-7qf9.