CVE-2023-37269 in Winter
Summary
by MITRE • 07/08/2023
Winter is a free, open-source content management system (CMS) based on the Laravel PHP framework. Users with the `backend.manage_branding` permission can upload SVGs as the application logo. Prior to version 1.2.3, SVG uploads were not sanitized, which could have allowed a stored cross-site scripting (XSS) attack. To exploit the vulnerability, an attacker would already need to have developer or super user level permissions in Winter CMS. This means they would already have extensive access and control within the system. Additionally, to execute the XSS, the attacker would need to convince the victim to directly visit the URL of the maliciously uploaded SVG, and the application would have to be using local storage where uploaded files are served under the same domain as the application itself instead of a CDN. This is because all SVGs in Winter CMS are rendered through an `img` tag, which prevents any payloads from being executed directly. These two factors significantly limit the potential harm of this vulnerability. This issue has been patched in v1.2.3 through the inclusion of full support for SVG uploads and automatic sanitization of uploaded SVG files. As a workaround, one may apply the patches manually.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 04/25/2025
The vulnerability CVE-2023-37269 affects Winter CMS, a free and open-source content management system built on the Laravel PHP framework. This security flaw resides in the application's handling of SVG file uploads, specifically within the backend branding management functionality. The vulnerability represents a stored cross-site scripting issue that could potentially compromise user sessions and enable attackers to execute malicious scripts in the context of the victim's browser. The flaw exists in versions prior to 1.2.3, where the system failed to properly sanitize SVG files uploaded by users with the `backend.manage_branding` permission level, creating a potential attack vector for malicious actors who have already gained sufficient privileges within the system.
The technical implementation of this vulnerability stems from inadequate input validation and sanitization processes within the file upload mechanism. When users with appropriate permissions upload SVG files, the system does not properly filter or sanitize the SVG content to remove potentially dangerous elements or attributes. This allows attackers to embed malicious code within SVG files that could execute when the images are rendered in web browsers. The vulnerability specifically affects the rendering process where uploaded SVGs are displayed through img tags, which prevents direct script execution but still allows for certain types of cross-site scripting attacks through SVG-specific vector elements. According to CWE classification, this vulnerability maps to CWE-79 - Improper Neutralization of Input During Web Page Generation, which addresses the failure to properly sanitize user-supplied data before it is used in web page generation.
The operational impact of this vulnerability is significantly limited by several mitigating factors that create substantial barriers for attackers attempting to exploit the flaw. The vulnerability requires an attacker to already possess developer or super user level permissions within the Winter CMS system, which represents a high privilege threshold that severely limits the attack surface. Additionally, successful exploitation requires the attacker to convince victims to directly visit the URL of the maliciously uploaded SVG file, and the application must be configured to serve uploaded files through local storage rather than a content delivery network. This domain-based restriction prevents the execution of malicious payloads through cross-domain attacks. The requirement for victims to directly access the SVG files also means that the vulnerability cannot be exploited through automated means or social engineering campaigns that rely on indirect user interactions.
The remediation for this vulnerability was implemented in Winter CMS version 1.2.3 through comprehensive SVG upload sanitization and validation mechanisms. The patch addresses the root cause by introducing full support for SVG uploads with automatic sanitization of uploaded SVG files, ensuring that potentially dangerous elements and attributes are removed or neutralized during the upload process. This approach aligns with security best practices outlined in the OWASP Top Ten and ATT&CK framework, particularly in the context of preventing server-side and client-side code injection vulnerabilities. Organizations can also apply manual patches as a workaround, though the official release provides a more robust and comprehensive solution. The fix demonstrates proper security engineering practices by implementing defense-in-depth measures that prevent the execution of malicious content through multiple vectors while maintaining the intended functionality of the SVG upload feature. The vulnerability's limited exploitability due to the high privilege requirements and specific environmental conditions makes it less critical compared to other vulnerabilities, but still requires prompt remediation to maintain overall system security posture.